Fibrillated fibers for liquid filtration media

ABSTRACT

Fiber webs which are used in filter media are described herein. In some embodiments, the fiber webs include fibrillated fibers and optionally non-fibrillated fibers, amongst other optional components (e.g., binder resin). In some embodiments, the fiber webs include limited amounts of, or no, glass fiber. The respective characteristics and amounts of the fibrillated fibers are selected to impart desirable properties including mechanical properties and filtration properties (e.g., dust holding capacity and efficiency), amongst other benefits.

RELATED APPLICATION

The present application is a continuation of U.S. patent applicationSer. No. 15/296,085, filed Oct. 18, 2016, which is a continuation ofU.S. patent application Ser. No. 14/135,187 (now U.S. Pat. No.9,511,330), filed Dec. 19, 2013, which is a continuation-in-part of U.S.patent application Ser. No. 13/528,774, filed on Jun. 20, 2012, whichare hereby incorporated by reference in their entirety.

FIELD OF INVENTION

Aspects described herein relate generally to fiber webs that includefibrillated fibers that can be used in filter media.

BACKGROUND

Filter media can be used to remove contamination in a variety ofapplications. In general, filter media include one or more fiber webs.The fiber web provides a porous structure that permits fluid (e.g.,fuel, lube, hydraulic fluid, air) to flow through the web. Contaminantparticles contained within the fluid may be trapped on the fiber web.Fiber web characteristics (e.g., fiber dimensions, fiber composition,basis weight, amongst others) affect mechanical properties (e.g.,elongation, strength, amongst others) and filtration performance (e.g.,dust holding capacity, liquid filtration efficiency, amongst others).

Certain filter media include webs that comprise glass fibers. Whileoften having desirable filtration performance, glass fiber webs mayexhibit limited strength and brittle characteristics which can lead tofiber shedding during handling, further processing (e.g., pleating,slitting), installation, and use. The presence of glass fibers in filtermedia may also give rise to environmental concerns.

In some applications, it would be desirable to limit the amount of glassfiber in a fiber web, while still achieving a desirable balance ofproperties including high filtration efficiency at a given pressure dropand/or high dust holding capacity, amongst others.

SUMMARY

Fibers webs that include fibrillated fibers and can be used in filtermedia are described herein.

In some embodiments, a series of filter media are provided. In one setof embodiments, a filter media comprises a wet laid fiber web comprisinga plurality of synthetic fibers. The wet laid fiber web has a [mean flowpore (μm)/(permeability (cfm/sf))^(0.5)] value of less than or equal toabout 3.0. Moreover, the wet laid fiber web comprises between about 0 wt% to about 10 wt % of glass fibers. The filter media has an basis weightof greater than about 10 g/m² and less than or equal to about 1000 g/m²,and a thickness of between about 0.1 mm and about 10.0 mm.

In another set of embodiments, a filter media comprises a fiber webcomprising a plurality of synthetic fibers. The fiber web has a [meanflow pore (μm)/(permeability (cfm/sf)^(0.5)] value of less than about3.0. Moreover, the fiber web has a dust holding capacity of greater thanor equal to about 80 g/m², wherein the dust holding capacity is measuredusing a Multipass Filter Tests at a 25 mg/L base upstream gravimetriclevel (BUGL), a face velocity of 0.06 cm/s, and a 100 kPa terminalpressure following the ISO 16889/19438 procedure. The wet laid fiber webcomprises between about 0 wt % to about 10 wt % of glass fibers.Additionally, the filter media has an basis weight of greater than about10 g/m² and less than or equal to about 1000 g/m² and a thickness ofbetween about 0.1 mm and about 10 mm.

In another set of embodiments, a filter media comprises a fiber webcomprising a plurality of fibrillated fibers. The fiber web comprisesabout 0 wt % to about 10 wt % of glass fibers. The filter media has aliquid filtration efficiency of at least 98% for 4 microns or greaterparticles, wherein the efficiency is measured using a Multipass FilterTests at a 25 mg/L base upstream gravimetric level (BUGL), a facevelocity of 0.06 cm/s, and a 100 kPa terminal pressure following the ISO16889/19438 procedure. Additionally, the filter media has a basis weightof greater than about 10 g/m² and less than or equal to about 1000 g/m²,and a thickness of between about 0.1 mm and about 10 mm.

In another set of embodiments, a filter media comprises a first layercomprising a plurality of organic polymer fibers, and a second layercomprising greater than or equal to about 60 wt % fibrillated fibers.The first layer has a first basis weight of greater than or equal toabout 10 g/m² and less than about 300 g/m². The second layer has asecond basis weight of greater than or equal to about 3 g/m² and lessthan about 200 g/m². The ratio of the first basis weight to the secondbasis weight is at least 3:1 and less than 14:1. The filter media has athickness of between about 0.3 mm and about 10 mm.

In another set of embodiments, a filter media comprises a first layerand a second layer in combination with an additional layer (e.g., athird layer). The first layer and/or second layer is a wet laid layer(e.g., a layer formed by a wet laid process). The additional layer is anon-wet laid layer (e.g., a layer formed by a non-wet laid process) andmay include meltblown fibers, meltspun fibers, centrifugal spun fibers,or fibers formed by other non-wet laid processes. The first layercomprises a plurality of organic polymer fibers, and the second layercomprises a plurality of synthetic fibers. At least one of the first andsecond layers includes fibrillated fibers (e.g., between about 1 wt %and about 100 wt % of the first and/or second layers). The first and/orsecond layers comprises between about 0 wt % to about 10 wt % of glassfibers. The additional layer includes synthetic polymer fibers. Thefilter media can achieve a fuel-water separation efficiency of at leastabout 30% (e.g., between about 60% to about 99.9%).

In certain embodiments described above and herein, the first and/orsecond layer may be a non-wet laid layer (e.g., formed of meltblownfibers, meltspun fibers, dry laid (carded) fibers, centrifugal spunfibers, spunbond fibers, and/or air laid fibers) as described herein.

In certain embodiments described above and herein, the additional layermay have a basis weight of between about 5 g/m² and about 800 g/m², anair permeability of less than about 1300 cfm/sf, and an average fiberdiameter of less than 100 microns. In certain embodiments describedabove and herein, the overall filter media may have a basis weight ofgreater than about 10 g/m² and less than or equal to about 1000 g/m², athickness of between about 0.1 mm and about 10.0 mm.

In certain embodiments described above and herein, the filter media canachieve an efficiency at 4 microns of at least 99%, an initialefficiency of at least 99%, and a dust holding capacity of at least 150gsm.

Other advantages and novel features of the present invention will becomeapparent from the following detailed description of various non-limitingembodiments of the invention when considered in conjunction with theaccompanying FIGURES. In cases where the present specification and adocument incorporated by reference include conflicting and/orinconsistent disclosure, the present specification shall control. If twoor more documents incorporated by reference include conflicting and/orinconsistent disclosure with respect to each other, then the documenthaving the later effective date shall control.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting embodiments of the present invention will be described byway of example with reference to the accompanying FIGURE, which isschematic and is not intended to be drawn to scale. In the FIGURE, eachidentical or nearly identical component illustrated is typicallyrepresented by a single numeral. For purposes of clarity, not everycomponent is labeled, nor is every component of each embodiment of theinvention shown where illustration is not necessary to allow those ofordinary skill in the art to understand the invention. In the FIGURES:

FIG. 1 is a schematic diagram showing a fiber web according to one setof embodiments.

DETAILED DESCRIPTION

Fiber webs which are used in filter media are described herein. In someembodiments, the fiber webs include fibrillated fibers and optionallynon-fibrillated fibers, amongst other optional components (e.g., binderresin). In some embodiments, the fiber webs include limited amounts of,or no, glass fiber. The respective characteristics and amounts of thefibrillated fibers are selected to impart desirable properties includingmechanical properties and filtration properties (e.g., dust holdingcapacity and efficiency), amongst other benefits. Filter media formed ofthe webs may be particularly well-suited for applications that involvefiltering fuel, though the media may also be used in other applications(e.g., for filtering lube, hydraulic fluids, air). In some embodiments,the fiber webs described herein may include multiple layers, thoughother arrangements are possible.

Advantageously, in some embodiments the use of fibrillated fibers canincrease the surface area of the fiber web, leading to an improvement inone or more properties of the media such as increased particle captureefficiency and/or dust holding capacity. The use of fibrillated fibersmay also lead to a decrease in the mean pore size of the fiber webcompared to a fiber web having similar properties (e.g., basis weight,fiber type, etc.) but absent fibrillated fibers. Accordingly, a fiberweb including such fibrillated fibers may have a relatively low pressuredrop while achieving an increased efficiency per unit thickness. In someembodiments, the fiber webs described herein can achieve such improvedproperties with limited amounts of, or no, glass fibers.

The fiber webs described herein may have a single layer, or multiplelayers. In some embodiments involving multiple layers, a cleardemarcation of layers may not always be apparent, as described in moredetail below. An example of a fiber web is shown in FIG. 1. As shownillustratively in FIG. 1, a fiber web 10 includes a first layer 15 and asecond layer 20 having a combined thickness 25. Optionally, the fiberweb may include additional layers (not shown). The first layer may bepositioned upstream or downstream of the second layer in a filterelement. In some embodiments, the first layer is a relatively open layer(e.g., having a relatively higher air permeability) compared to thesecond layer, and the second layer is a relatively tight layer (e.g.,having a relatively lower air permeability) compared to the first layer.In other embodiments, the first layer is a relatively tight layercompared to the first layer, and the second layer is a relatively openlayer compared to the second layer.

As described in more detail below, one or more fibrillated fibers may bepresent in at least one layer of the fiber web, such as in the firstlayer, in the second layer, in both layers, or in all layers. In someembodiments, the first layer may be constructed to have a relativelyhigh dust holding capacity. The first layer may also be constructed tohave a relatively high filtration efficiency in some cases. The firstlayer may include fibrillated fibers in some embodiments, but does notinclude fibrillated fibers in other embodiments. In some instances, thefirst layer may be positioned upstream of the second layer in a filterelement. In some embodiments, the second layer includes one or morefibrillated fibers and is constructed to achieve a relatively highfiltration efficiency. The second layer may also have good dust holdingproperties in some embodiments. The second layer may be positioneddownstream of the first layer in a filter element. As described in moredetail below, the properties of the fiber web may be tailored by varyingthe amount of fibrillated fibers, the type of fibrillated fibers, and/orthe level of fibrillation of the fibers present in one or more layers ofthe fiber web. Examples of suitable types, amounts, and levels offibrillation for fibrillated fibers in each of the layers are providedbelow.

It should be appreciated that while FIG. 1 shows only first and secondlayers, other layers may be present in other embodiments. For example, afiber web may include a third layer positioned directly adjacent thefirst layer (e.g., on the side opposite the second layer), directlyadjacent the second layer (e.g., on the side opposite the first layer),or between the first and second layers. Additional layers are alsopossible. In certain embodiments, an additional layer (e.g., a thirdlayer, a fourth layer, etc.) may be used to enhance one or more of dustholding capacity, lifetime, liquid filtration efficiency, waterseparation efficiency, and/or strength (e.g., Mullen burst strength,tensile strength, elongation) in the fiber web, as described in moredetail below. Moreover, it should be appreciated that any additionallayers (e.g., a third layer, a fourth layer, etc.) may have any of thefeatures or properties described herein for the first or second layers.

In some embodiments, fiber web 10 includes a clear demarcation betweenthe first and second layers. For example, the fiber web may include aninterface 40 between the two layers that is distinct. In some suchembodiments, the first and second layers may be formed separately, andcombined by any suitable method such as lamination, collation, or by useof adhesives. The first and second layers (and any additional layer(s))may be formed using different processes, or the same process. Forexample, each of the first and second layers (and any additionallayer(s)) may be independently formed by a wet laid process, a non-wetlaid process (e.g., a dry laid process, a spinning process, a meltblownprocess), or any other suitable process.

In other embodiments, fiber web 10 does not include a clear demarcationbetween the first and second layers. For example, a distinct interfacebetween the two layers may not be apparent. In some cases, the layersforming a fiber web may be indistinguishable from one another across thethickness of the fiber web. The first and second layers may be formed bythe same process (e.g., a wet laid process, a non-wet laid process(e.g., a dry laid process, a spinning process, a meltblown process), orany other suitable process) or by different processes in suchembodiments. In some instances, the first and second layers may beformed simultaneously.

Regardless of whether a clear demarcation between first and secondlayers is present, in some embodiments, fiber web 10 includes a gradient(i.e., a change) in one or more properties such as amount of fibrillatedfiber, level of fibrillation of fibers, fiber diameter, fiber type,fiber composition, fiber length, fiber surface chemistry, pore size,material density, basis weight, solidity, a proportion of a component(e.g., a binder, resin, crosslinker), stiffness, tensile strength,wicking ability, hydrophilicity/hydrophobicity, and conductivity acrossa portion, or all of, the thickness of the fiber web. Fiber webssuitable for use as filter media may optionally include a gradient inone or more performance characteristics such as efficiency, dust holdingcapacity, pressure drop, permeability, and porosity across the thicknessof the fiber web. A gradient in one or more such properties may bepresent in the fiber web between a top surface 30 and a bottom surface35 of the fiber web.

Different types and configurations of gradients are possible within afiber web. In some embodiments, a gradient in one or more properties isgradual (e.g., linear, curvilinear) between a top surface and a bottomsurface of the fiber web. For example, the fiber web may have anincreasing amount of fibrillated fiber from the top surface to thebottom surface of the fiber web. In another embodiment, a fiber web mayinclude a step gradient in one more properties across the thickness ofthe fiber web. In one such embodiment, the transition in the propertymay occur primarily at interface 40 between the two layers. For example,a fiber web, e.g., having a first layer including a first fiber type anda second layer including a second fiber type, may have an abrupttransition between fiber types across the interface. In other words,each of the layers of the fiber web may be relatively distinct. Othertypes of gradients are also possible.

In certain embodiments, a fiber web may include a gradient in one ormore properties through portions of the thickness of the fiber web. Inthe portions of the fiber web where the gradient in the property is notpresent, the property may be substantially constant through that portionof the web. As described herein, in some instances a gradient in aproperty involves different proportions of a component (e.g., a type offiber such as a fibrillated fiber, hardwood fibers, softwood fibers, anadditive, a binder) across the thickness of a fiber web. In someembodiments, a component may be present at an amount or a concentrationthat is different than another portion of the fiber web. In otherembodiments, a component is present in one portion of the fiber web, butis absent in another portion of the fiber web. Other configurations arealso possible.

In some embodiments, a fiber web has a gradient in one or moreproperties in two or more regions of the fiber web. For example, a fiberweb including three layers may have a first gradient in one propertyacross the first and second layer, and a second gradient in anotherproperty across the second and third layers. The first and secondgradients may be the same in some embodiments, or different in otherembodiments (e.g., characterized by a gradual vs. an abrupt change in aproperty across the thickness of the fiber web). Other configurationsare also possible.

A fiber web may include any suitable number of layers, e.g., at least 2,3, 4, 5, 6, 7, 8, or 9 layers depending on the particular applicationand performance characteristics desired. It should be appreciated thatin some embodiments, the layers forming a fiber web may beindistinguishable from one another across the thickness of the fiberweb. As such, a fiber web formed from, for example, two “layers” or two“fiber mixtures” can also be characterized as having a single “layer”(or a “composite” layer) having a gradient in a property across thefiber web in some instances. Such composite layers may optionally becombined with additional layers in the fiber web to form, for example,fiber webs having a gradient in one or more properties in certainportions of the fiber web, but not in other portions of the fiber web.

For example, in one set of embodiments, the first layer of fiber web 10of FIG. 1 does not include a gradient of a property across the thicknessof the first layer, but the second layer does include a gradient of aproperty across the thickness of the second layer. In another example,the first layer of fiber web 10 of FIG. 1 includes a gradient of aproperty across the thickness of the first layer, but the second layerdoes not include a gradient of a property across the thickness of thesecond layer. In other embodiments, both the first layer and the secondlayer includes a gradient of one or more properties across thethicknesses of the layers. Other configurations are also possible. Asdescribed herein, the one or more properties varying across thethickness of a layer may include, for example, a concentration of afibrillated fiber, level of fibrillation of fibers, fiber type (e.g.,type of fibrillated fiber), fiber diameter, fiber composition, fiberlength, fiber surface chemistry, pore size, material density, basisweight, solidity, a proportion of a component (e.g., a binder, resin,crosslinker), stiffness, tensile strength, wicking ability,hydrophilicity/hydrophobicity, and/or conductivity.

As noted above, the fiber webs described herein include one or morefibrillated fibers. As known to those of ordinary skill in the art, afibrillated fiber includes a parent fiber that branches into smallerdiameter fibrils which can, in some instances, branch further out intoeven smaller diameter fibrils with further branching also beingpossible. The branched nature of the fibrils leads to a fiber web havinga high surface area and can increase the number of contact pointsbetween the fibrillated fibers and other fibers in the web. Such anincrease in points of contact between the fibrillated fibers and otherfibers and/or components of the web may contribute to enhancingmechanical properties (e.g., flexibility, strength) and/or filtrationperformance properties of the fiber web.

In general, the fibrillated fibers included in a fiber web may have anysuitable level of fibrillation. The level of fibrillation relates to theextent of branching in the fiber. In some embodiments, the average levelof fibrillation of fibers may vary between different layers in amulti-layered fiber web. For example, a first layer may include fibershaving a relatively low level of fibrillation compared to the fibers ofa second layer. In other embodiments, a first layer may include fibershaving a relatively high level of fibrillation compared to the fibers ofa second layer.

The average level of fibrillation may vary in a layer (or vary in theentire web) depending on whether the layer (or web) includes a singletype of fibrillated fiber or more than one type of fibrillated fiber.The same fiber type, but fibers fibrillated to different extents, mayalso be used in one or more layers of the fiber web.

The level of fibrillation may be measured according to any number ofsuitable methods. For example, the level of fibrillation of thefibrillated fibers can be measured according to a Canadian StandardFreeness (CSF) test, specified by TAPPI test method T 227 om 09 Freenessof pulp. The test can provide an average CSF value. In some embodiments,the average CSF value of the fibrillated fibers used in a fiber web mayvary between about 10 mL and about 750 mL. In certain embodiments, theaverage CSF value of the fibrillated fibers used in a fiber web may begreater than or equal to 1 mL, greater than or equal to about 10 mL,greater than or equal to about 20 mL, greater than or equal to about 35mL, greater than or equal to about 45 mL, greater than or equal to about50 mL, greater than or equal to about 65 mL, greater than or equal toabout 70 mL, greater than or equal to about 75 mL, greater than or equalto about 80 mL, greater than or equal to about 100 mL, greater than orequal to about 150 mL, greater than or equal to about 175 mL, greaterthan or equal to about 200 mL, greater than or equal to about 250 mL,greater than or equal to about 300 mL, greater than or equal to about350 mL, greater than or equal to about 500 mL, greater than or equal toabout 600 mL, greater than or equal to about 650 mL, greater than orequal to about 700 mL, or greater than or equal to about 750 mL.

In some embodiments, the average CSF value of the fibrillated fibersused in a fiber web may be less than or equal to about 800 mL, less thanor equal to about 750 mL, less than or equal to about 700 mL, less thanor equal to about 650 mL, less than or equal to about 600 mL, less thanor equal to about 550 mL, less than or equal to about 500 mL, less thanor equal to about 450 mL, less than or equal to about 400 mL, less thanor equal to about 350 mL, less than or equal to about 300 mL, less thanor equal to about 250 mL, less than or equal to about 225 mL, less thanor equal to about 200 mL, less than or equal to about 150 mL, less thanor equal to about 100 mL, less than or equal to about 90 mL, less thanor equal to about 85 mL, less than or equal to about 70 mL, less than orequal to about 50 mL, less than or equal to about 40 mL, or less than orequal to about 25 mL. Combinations of the above-referenced ranges arealso possible (e.g., an average CSF value of fibrillated fibers ofgreater than or equal to about 10 mL and less than or equal to about 300mL). Other ranges are also possible. The average CSF value of thefibrillated fibers used in a fiber web may be based on one type offibrillated fiber or more than one type of fibrillated fiber.

In some embodiments, the level of fibrillation of the fibrillated fiberscan be measured according to a Schopper Riegler (SR) test. In someembodiments, the average SR value of the fibrillated fibers may begreater than about 20° SR, greater than about 30° SR, greater than about40° SR, greater than about 50° SR, or greater than about 60° SR. In someembodiments, the average SR value of the fibrillated fibers may be lessthan about 80° SR, less than about 70° SR, less than about 60° SR, lessthan about 50° SR, or less than about 40° SR. It can be appreciated thatthe average SR values may be between any of the above-noted lower limitsand upper limits. For example, the average SR value of the fibrillatedfibers may be between about 20° SR and about 70° SR, between about 20°SR and about 60° SR, or between about 30° SR and about 50° SR, betweenabout 32° SR and about 52° SR, or between about 40° SR and about 50° SR.

It should be understood that, in certain embodiments, the fibers mayhave fibrillation levels outside the above-noted ranges.

In embodiments in which the fiber web includes at least first and secondlayers, such as in the embodiment shown illustratively in FIG. 1, theaverage CSF value of fibrillated fibers (if present) in each of thelayers may vary. For example, if fibrillated fibers are included in thefirst layer, the average CSF value of the fibrillated fibers in thefirst layer may vary between about 10 mL and about 750 mL. In certainembodiments, the average CSF value of the fibrillated fibers used in afirst layer may be greater than or equal to 1 mL, greater than or equalto about 10 mL, greater than or equal to about 20 mL, greater than orequal to about 35 mL, greater than or equal to about 45 mL, greater thanor equal to about 50 mL, greater than or equal to about 65 mL, greaterthan or equal to about 70 mL, greater than or equal to about 75 mL,greater than or equal to about 80 mL, greater than or equal to about 100mL, greater than or equal to about 150 mL, greater than or equal toabout 175 mL, greater than or equal to about 200 mL, greater than orequal to about 250 mL, greater than or equal to about 300 mL, greaterthan or equal to about 350 mL, greater than or equal to about 500 mL,greater than or equal to about 600 mL, greater than or equal to about650 mL, greater than or equal to about 700 mL, or greater than or equalto about 750 mL.

In some embodiments, the average CSF value of the fibrillated fibersused in a first layer may be less than or equal to about 750 mL, lessthan or equal to about 700 mL, less than or equal to about 650 mL, lessthan or equal to about 600 mL, less than or equal to about 550 mL, lessthan or equal to about 500 mL, less than or equal to about 450 mL, lessthan or equal to about 400 mL, less than or equal to about 350 mL, lessthan or equal to about 300 mL, less than or equal to about 250 mL, lessthan or equal to about 225 mL, less than or equal to about 200 mL, lessthan or equal to about 150 mL, less than or equal to about 100 mL, lessthan or equal to about 90 mL, less than or equal to about 85 mL, lessthan or equal to about 70 mL, less than or equal to about 50 mL, lessthan or equal to about 40 mL, or less than or equal to about 25 mL.Combinations of the above-referenced ranges are also possible (e.g., anaverage CSF value of fibrillated fibers of greater than or equal toabout 10 mL and less than or equal to about 300 mL). Other ranges arealso possible. The average CSF value of the fibrillated fibers used in afirst layer may be based on one type of fibrillated fiber or more thanone type fibrillated fiber.

If fibrillated fibers are included in the second layer, the average CSFvalue of the fibrillated fibers in the second layer may vary betweenabout 10 mL and about 750 mL. In certain embodiments, the average CSFvalue of the fibrillated fibers used in a second layer may be greaterthan or equal to 1 mL, greater than or equal to about 10 mL, greaterthan or equal to about 20 mL, greater than or equal to about 35 mL,greater than or equal to about 45 mL, greater than or equal to about 50mL, greater than or equal to about 65 mL, greater than or equal to about70 mL, greater than or equal to about 75 mL, greater than or equal toabout 80 mL, greater than or equal to about 100 mL, greater than orequal to about 150 mL, greater than or equal to about 175 mL, greaterthan or equal to about 200 mL, greater than or equal to about 250 mL,greater than or equal to about 300 mL, greater than or equal to about350 mL, greater than or equal to about 500 mL, greater than or equal toabout 600 mL, greater than or equal to about 650 mL, greater than orequal to about 700 mL, or greater than or equal to about 750 mL.

In some embodiments, the average CSF value of the fibrillated fibersused in a second layer may be less than or equal to about 750 mL, lessthan or equal to about 700 mL, less than or equal to about 650 mL, lessthan or equal to about 600 mL, less than or equal to about 550 mL, lessthan or equal to about 500 mL, less than or equal to about 450 mL, lessthan or equal to about 400 mL, less than or equal to about 350 mL, lessthan or equal to about 300 mL, less than or equal to about 250 mL, lessthan or equal to about 225 mL, less than or equal to about 200 mL, lessthan or equal to about 150 mL, less than or equal to about 100 mL, lessthan or equal to about 90 mL, less than or equal to about 85 mL, lessthan or equal to about 70 mL, less than or equal to about 50 mL, lessthan or equal to about 40 mL, or less than or equal to about 25 mL.Combinations of the above-referenced ranges are also possible (e.g., anaverage CSF value of fibrillated fibers of greater than or equal toabout 10 mL and less than or equal to about 300 mL). Other ranges arealso possible. The average CSF value of the fibrillated fibers used in asecond layer may be based on one type of fibrillated fiber or more thanone type fibrillated fiber.

A fibrillated fiber may be formed of any suitable materials such assynthetic materials (e.g., synthetic polymers such as polyester,polyamide, polyaramid, para-aramid, meta-aramid, polyimide,polyethylene, polypropylene, polyether ether ketone, polyethyleneterephthalate, polyolefin, nylon, acrylics, regenerated cellulose (e.g.,lyocell, rayon), liquid crystal polymers (e.g., polyp-phenylene-2,6-bezobisoxazole (PBO), polyester-based liquid crystalpolymers such as polyesters produced by the polycondensation of4-hydroxybenzoic acid and 6-hydroxynaphthalene-2-carboxylic acid), andnatural materials (e.g., natural polymers such as cellulose (e.g.,non-regenerated cellulose), organic fibers such as wool). In someembodiments, organic polymer fibers are used. In certain embodiments,carbon fibers are used.

In some embodiments, fibrillated fibers may be synthetic fibers.Synthetic fibers as used herein, are non-naturally occurring fibersformed of polymeric material. Fibrillated fibers may also benon-synthetic fibers, for example, cellulose fibers that are naturallyoccurring. Cellulose fibers may include, for example, wood cellulosefibers and non-wood cellulose fibers. It can be appreciated thatfibrillated fibers may include any suitable combination of syntheticand/or non-synthetic fibers.

In certain embodiments, the fibrillated fibers are formed of lyocell.Lyocell fibers are known to those of skill in the art as a type ofsynthetic fiber and may be produced from regenerated cellulose bysolvent spinning.

In certain embodiments, the fibrillated fibers are formed of rayon.Rayon fibers are known to those of ordinary skill in the art. They arealso produced from regenerated cellulose and may be produced using anacetate method, a cuprammonium method, or a viscose process. In thesemethods, the cellulose or cellulose solution may be spun to form fibers.

Fibers may be fibrillated through any appropriate fibrillationrefinement process. In some embodiments, fibers are fibrillated using adisc refiner, a stock beater or any other suitable fibrillatingequipment.

It should be understood that, in certain embodiments, the fibrillatedfibers may have compositions other than those described above. Forexample, suitable compositions may include acrylic, liquid crystallinepolymers, polyoxazole (e.g., poly(p-phenylene-2,6-benzobisoxazole),aramid, paramid, cellulose wood, cellulose non-wood, cotton,polyethylene, polyolefin and olefin, amongst others.

In general, the fibrillated fibers may have any suitable dimensions(e.g., dimensions measured via a microscope).

As noted above, fibrillated fibers include parent fibers and fibrils.The parent fibers may have an average diameter of, for example, betweenabout 1 micron about 75 microns. In some embodiments, the parent fibersmay have an average diameter of less than or equal to about 75 microns,less than or equal to about 60 microns, less than or equal to about 50microns, less than or equal to about 40 microns, less than or equal toabout 30 microns, less than or equal to about 20 microns, or less thanor equal to about 15 microns. In some embodiments the parent fibers mayhave an average diameter of greater than or equal to about 10 microns,greater than or equal to about 15 microns, greater than or equal toabout 20 microns, greater than or equal to about 30 microns, greaterthan or equal to about 40 microns, greater than or equal to about 50microns, greater than or equal to about 60 microns, or greater than orequal to about 75 microns. Combinations of the above referenced rangesare also possible (e.g., parent fibers having an average diameter ofgreater than or equal to about 15 microns and less than about 75microns). Other ranges are also possible.

The fibrils may have an average diameter of, for example, between about0.2 micron about 15 microns. In some embodiments, the fibrils may havean average diameter of less than or equal to about 15 microns, less thanor equal to about 10 microns, less than or equal to about 8 microns,less than or equal to about 6 microns, less than or equal to about 4microns, less than or equal to about 3 microns, less than or equal toabout 2 microns, or less than or equal to about 1 micron. In someembodiments the fibrils may have an average diameter of greater than orequal to about 0.2 microns, greater than or equal to about 1 micron,greater than or equal to about 2 microns, greater than or equal to about3 microns, greater than or equal to about 4 microns, greater than orequal to about 6 microns, greater than or equal to about 8 microns, orgreater than or equal to about 10 microns. Combinations of the abovereferenced ranges are also possible (e.g., fibrils having an averagediameter of greater than or equal to about 3 microns and less than about6 microns). Other ranges are also possible.

The fibrillated fibers described may have an average length of, forexample, between about 1 mm and about 15 mm (e.g., between about 0.2 andabout 12 mm, or between about 2 mm and about 4 mm). In some embodiments,the average length of a fibrillated fiber may be less than or equal toabout 15 mm, less than or equal to about 12 mm, less than or equal toabout 10 mm, less than or equal to about 8 mm, less than or equal toabout 6 mm, less than or equal to about 4 mm, or less than or equal toabout 2 mm. In certain embodiments, the average length of a fibrillatedfiber may be greater than or equal to about 2 mm, greater than or equalto about 4 mm, greater than or equal to about 6 mm, greater than orequal to about 8 mm, greater than equal to about 10 mm, or greater thanor equal to about 12 mm. Combinations of the above referenced ranges arealso possible (e.g., fibrillated fibers having an average length ofgreater than or equal to about 2 mm and less than about 12 mm). Otherranges are also possible. The average length of the fibrillated fibersrefers to the average length of parent fibers from one end to anopposite end of the parent fibers. In some embodiments, the maximumaverage length of the fibrillated fibers fall within the above-notedranges. The maximum average length refers to the average of the maximumdimension along one axis of the fibrillated fibers (including parentfibers and fibrils).

The above-noted dimensions may be, for example, when the fibrillatedfibers are lyocell or when the fibrillated fibers are a material otherthan lyocell. It should be understood that, in certain embodiments, thefibers and fibrils may have dimensions outside the above-noted ranges.

In general, the fiber web may include any suitable weight percentage offibrillated fibers to achieve the desired balance of properties. In someembodiments, the weight percentage of the fibrillated fibers in thefiber web is between about 1 wt % and about 100 wt % (e.g., betweenabout 2 wt % and about 60 wt %). For instance, the weight percentage offibrillated fibers in the fiber web may be greater than or equal toabout 2 wt %, greater than or equal to about 5 wt %, greater than orequal to about 10 wt %, greater than or equal to about 15 wt %, greaterthan or equal to about 20 wt %, greater than or equal to about 25 wt %,greater than or equal to about 30 wt %, greater than or equal to about35 wt %, greater than or equal to about 40 wt %, greater than or equalto about 45 wt %, greater than or equal to about 50 wt %, or greaterthan or equal to about 60 wt %. In some embodiments, the weightpercentage of the fibrillated fibers in the web is less than or equal toabout 100 wt %, less than or equal to about 90 wt %, less than or equalto about 80 wt %, less than or equal to about 70 wt %, less than orequal to about 60 wt %, less than or equal to about 55 wt %, less thanor equal to about 50 wt %, less than or equal to about 45 wt %, lessthan or equal to about 40 wt %, less than or equal to about 35 wt %,less than or equal to about 30 wt %, less than or equal to about 25 wt%, less than or equal to about 20 wt %, less than or equal to about 15wt %, less than or equal to about 10 wt %, or less than or equal toabout 5 wt %. Combinations of the above-referenced ranges are alsopossible (e.g., a weight percentage of greater than about 2 wt % andless than or equal to about 25 wt %). Other ranges are also possible.

In some embodiments, fiber webs having an amount of fibrillated fibersthat is greater than that of other fiber webs may exhibit acomparatively greater degree of flexibility and strength, for example,an increased elongation, tensile strength and/or burst strength than theother fiber webs.

In certain embodiments, a fiber web or a layer within a fiber web (e.g.,a first layer or a second layer) includes fibrillated fibers having arelatively high degree of fibrillation. In some such embodiments, loweramounts of fibrillated fiber may be needed in order to achieve the samestructural and/or performance characteristics as a fiber web includingfibrillated fibers having a relatively lower degree of fibrillation butlarger amounts of such fibers. In certain embodiments, a fiber web or alayer within a fiber web (e.g., a first layer or a second layer)includes fibrillated fibers having an average CSF value of greater thanor equal to about 10 mL and less than or equal to about 300 mL, lessthan or equal to about 250 mL, less than or equal to about 225 mL, lessthan or equal to about 200 mL, less than or equal to about 150 mL, lessthan or equal to about 100 mL, less than or equal to about 90 mL, lessthan or equal to about 85 mL, less than or equal to about 70 mL, lessthan or equal to about 50 mL, less than or equal to about 40 mL, or lessthan or equal to about 25 mL. The weight percentage of fibrillatedfibers in such a fiber web or layer within the fiber web may be, forexample, greater than or equal to about 2 wt % (e.g., greater than orequal to about 5 wt %, greater than or equal to about 10 wt %, greaterthan or equal to about 15 wt %, greater than or equal to about 20 wt %,greater than or equal to about 25 wt %, greater than or equal to about30 wt %, greater than or equal to about 35 wt %, greater than or equalto about 40 wt %, greater than or equal to about 45 wt %, greater thanor equal to about 50 wt %, greater than or equal to about 60 wt %.greater than or equal to about 70 wt %, greater than or equal to about80 wt %) and less than or equal to about 90 wt %, less than or equal toabout 80 wt %, less than or equal to about 70 wt %, less than or equalto about 60 wt %, less than or equal to about 55 wt %, less than orequal to about 50 wt %, less than or equal to about 45 wt %, less thanor equal to about 40 wt %, less than or equal to about 35 wt %, lessthan or equal to about 30 wt %, less than or equal to about 25 wt %,less than or equal to about 20 wt %, less than or equal to about 15 wt%, less than or equal to about 10 wt %, or less than or equal to about 5wt %. Other ranges are also possible.

In embodiments in which a fiber web includes at least first and secondlayers, such as in the embodiment shown illustratively in FIG. 1, theweight percentage of fibrillated fibers in each of the layers may alsovary. For example, in some embodiments, the weight percentage offibrillated fibers in the first layer may be between about 0 wt % andabout 100 wt %. In some embodiments, the weight percentage offibrillated fibers in the first layer of the fiber web may be greaterthan or equal to about 2 wt %, greater than or equal to about 10 wt %,greater than or equal to about 20 wt %, greater than or equal to about40 wt %, greater than or equal to about 60 wt %, or greater than orequal to about 80 wt %. In some embodiments, the weight percentage ofthe fibrillated fibers in the first layer may be less than or equal toabout 100 wt %, less than or equal to about 80 wt %, less than or equalto about 40 wt %, less than or equal to about 20 wt %, less than orequal to about 10 wt %, or less than or equal to about 5 wt %.Combinations of the above-referenced ranges are also possible (e.g., aweight percentage of greater than about 2 wt % and less than or equal toabout 100 wt %). Other ranges are also possible.

In some embodiments, the weight percentage of fibrillated fibers in thesecond layer may be between about 0 wt % and about 100 wt %. In someembodiments, the weight percentage of fibrillated fibers in the secondlayer of the fiber web may be greater than or equal to about 1 wt %,greater than or equal to about 2 wt %, greater than or equal to about 5wt %, greater than or equal to about 10 wt %, greater than or equal toabout 20 wt %, greater than or equal to about 30 wt %, greater than orequal to about 40 wt %, greater than or equal to about 50 wt %, greaterthan or equal to about 60 wt %, greater than or equal to about 70 wt %,greater than or equal to about 80 wt %, or greater than or equal toabout 90 wt %. In some embodiments, the weight percentage of thefibrillated fibers in the second layer may be less than or equal toabout 100 wt %, less than or equal to about 90 wt %, less than or equalto about 80 wt %, less than or equal to about 70 wt %, less than orequal to about 60 wt %, less than or equal to about 50 wt %, less thanor equal to about 40 wt %, less than or equal to about 30 wt %, lessthan or equal to about 20 wt %, less than or equal to about 15 wt %,less than or equal to about 10 wt %, or less than or equal to about 5 wt%. Combinations of the above-referenced ranges are also possible (e.g.,a weight percentage of greater than about 5 wt % and less than or equalto about 100 wt %). Other ranges are also possible.

As noted above, the amount of fibrillated fibers and the level offibrillation may vary between fiber web layers of the filter media. Forexample, the relative amount of fibrillated fibers and the level offibrillation may vary when a first layer of a filter media is anupstream layer and a second layer of the filter media is a downstreamlayer. In some embodiments, an upstream layer has a lesser degree offibrillation (i.e., greater average CSF) than a downstream layer. Inother embodiments, an upstream layer has a greater degree offibrillation than a downstream layer. In some embodiments, thepercentage of fibrillated fibers in an upstream layer is comparativelysmaller than the percentage of fibrillated fibers in a downstream layer.In other embodiments, the percentage of fibrillated fibers in anupstream layer is greater than the percentage of fibrillated fibers in adownstream layer.

In certain embodiments in which a fiber web including at least first andsecond layers, the second layer may include more fibrillated fibers thanthe first layer (e.g., at least 10%, at least 20%, at least 40%, atleast 60%, at least 80%, at least 100%, at least 150%, at least 200%, atleast 300%, at least 400%, at least 500%, or at least 1000% morefibrillated fibers than the first layer). In other embodiments, thefirst layer may include more fibrillated fibers than the second layer(e.g., at least 10%, at least 20%, at least 40%, at least 60%, at least80%, at least 100%, at least 150%, at least 200%, at least 300%, atleast 400%, at least 500%, or at least 1000% more fibrillated fibersthan the second layer). Other ranges are also possible. In some cases,the same amount of fibrillated fibers are present in each of the layers.Gradients of amounts of fibrillated fibers may also be present acrossthe thickness of the fiber web.

In some embodiments in which a fiber web including at least first andsecond layers, the second layer may include fibrillated fibers having ahigher average level of fibrillation than the fibrillated fibers of thefirst layer. For example, the average CSF value of the fibrillatedfibers of the second layer may be at least 10%, at least 20%, at least40%, at least 60%, at least 80%, at least 100%, at least 150%, at least200%, at least 300%, at least 400%, or at least 500% greater than theaverage CSF value of the fibrillated fibers of the first layer. In otherembodiments, the first layer may include fibrillated fibers having ahigher average level of fibrillation than the fibrillated fibers of thesecond layer. For example, the average CSF value of the fibrillatedfibers of the first layer may be at least 10%, at least 20%, at least40%, at least 60%, at least 80%, at least 100%, at least 150%, at least200%, at least 300%, at least 400%, or at least 500% greater than theaverage CSF value of the fibrillated fibers of the second layer. Otherranges are also possible. In some cases, the fibrillated fibers in eachof the layers has the same level of fibrillation. Gradients of averagelevels of fibrillation may also be present across the thickness of thefiber web.

In some cases, it may be advantageous for the fibrillated fibers to bealigned in the machine direction of the web (i.e., when a fiber's lengthextends substantially in the machine direction) and/or in thecross-machine direction of the web (i.e., when a fiber's length extendssubstantially in the cross-machine direction). It should be understoodthat the terms “machine direction” and “cross-machine” direction havetheir usual meanings in the art. That is, the machine direction refersto the direction in which the fiber web moves along the processingmachine during processing and the cross-machine direction refers to adirection perpendicular to the machine direction.

In some embodiments, the fiber webs described herein may includecellulose fibers. As described herein, the cellulose fibers may befibrillated or non-fibrillated. Mixtures of fibrillated andnon-fibrillated cellulose fibers are also possible. The cellulose fibersmay include any suitable type of cellulose fibers such as softwoodfibers, hardwood fibers, and mixtures thereof. Moreover, the cellulosefibers may include natural cellulose fibers, synthetic cellulose fibers(e.g., regenerated cellulose), or mixtures thereof.

The fiber web may include a suitable percentage of cellulose fibers. Forexample, in some embodiments, the weight percentage of cellulose fibersin the fiber web may be between about 0 wt % and about 100 wt %. In someembodiments, the weight percentage of cellulose fibers in the fiber webmay be greater than or equal to about 5 wt %, greater than or equal toabout 10 wt %, greater than or equal to about 30 wt %, greater than orequal to about 50 wt %, greater than or equal to about 70 wt %, greaterthan or equal to about 80 wt %, greater than or equal to about 90 wt %,greater than or equal to about 95 wt %, or greater than or equal toabout 98 wt %. In some embodiments, the weight percentage of thecellulose fibers in the fiber web may be less than or equal to about 100wt %, less than or equal to about 98 wt %, less than or equal to about95 wt %, less than or equal to about 90 wt %, less than or equal toabout 80 wt %, less than or equal to about 70 wt %, less than or equalto about 50 wt %, less than or equal to about 40 wt %, less than orequal to about 20 wt %, less than or equal to about 10 wt %, or lessthan or equal to about 5 wt %. Combinations of the above-referencedranges are also possible (e.g., a weight percentage of greater thanabout 5 wt % and less than or equal to about 80 wt %). Other ranges arealso possible. In some embodiments, a fiber web includes 0 wt % ofcellulose fibers. In other embodiments, a fiber web includes 100 wt % ofcellulose fibers.

In embodiments in which the fiber web includes at least first and secondlayers, such as in the embodiment shown illustratively in FIG. 1, theweight percentage of cellulose fibers in each of the layers may alsovary. For example, in some embodiments, the weight percentage ofcellulose fibers in the first layer of the fiber web may be betweenabout 0 wt % and about 100 wt %. In some embodiments, the weightpercentage of cellulose fibers in the first layer of the fiber web maybe greater than or equal to about 10 wt %, greater than or equal toabout 30 wt %, greater than or equal to about 50 wt %, greater than orequal to about 70 wt %, greater than or equal to about 80 wt %, greaterthan or equal to about 90 wt %, or greater than or equal to about 95 wt%. In some embodiments, the weight percentage of cellulose fibers in thefirst layer of the fiber web may be less than or equal to about 100 wt%, less than or equal to about 95 wt %, less than or equal to about 90wt %, less than or equal to about 80 wt %, less than or equal to about70 wt %, less than or equal to about 50 wt %, or less than or equal toabout 40 wt %, less than or equal to about 20 wt %, or less than orequal to about 10 wt %. Combinations of the above-referenced ranges arealso possible (e.g., a weight percentage of greater than about 5 wt %and less than or equal to about 80 wt %). Other ranges are alsopossible. In some embodiments, the first layer of the fiber web includes0 wt % of cellulose fibers. In other embodiments, the first layer of thefiber web includes 100 wt % of cellulose fibers.

In some embodiments, the weight percentage of cellulose fibers in thesecond layer of the fiber web may be between about 0 wt % and about 100wt %. In some embodiments, the weight percentage of cellulose fibers inthe second layer of the fiber web may be greater than or equal to about5 wt %, greater than or equal to about 10 wt %, greater than or equal toabout 30 wt %, greater than or equal to about 50 wt %, greater than orequal to about 70 wt %, greater than or equal to about 80 wt %, greaterthan or equal to about 90 wt %, or greater than or equal to about 95 wt%. In some embodiments, the weight percentage of cellulose fibers in thesecond layer of the fiber web may be less than or equal to about 100 wt%, less than or equal to about 95 wt %, less than or equal to about 90wt %, less than or equal to about 80 wt %, less than or equal to about70 wt %, less than or equal to about 50 wt %, or less than or equal toabout 40 wt %, less than or equal to about 20 wt %, or less than orequal to about 10 wt %. Combinations of the above-referenced ranges arealso possible (e.g., a weight percentage of greater than about 5 wt %and less than or equal to about 80 wt %). Other ranges are alsopossible. In some embodiments, the second layer of the fiber webincludes 0 wt % of cellulose fibers. In other embodiments, the secondlayer of the fiber web includes 100 wt % of cellulose fibers.

A fiber web may include any suitable amount of hardwood and/or softwoodfibers, which may be fibrillated or non-fibrillated. Mixtures offibrillated and non-fibrillated hardwood and/or softwood fibers are alsopossible.

In some embodiments, the weight percentage of hardwood fibers in thefiber web may be between about 0 wt % and about 98 wt %. In someembodiments, the weight percentage of hardwood fibers in the fiber webmay be greater than or equal to about 5 wt %, greater than or equal toabout 10 wt %, greater than or equal to about 30 wt %, greater than orequal to about 50 wt %, greater than or equal to about 70 wt %, greaterthan or equal to about 80 wt %, greater than or equal to about 90 wt %,or greater than or equal to about 98 wt %. In some embodiments, theweight percentage of the hardwood fibers in the fiber web may be lessthan or equal to about 98 wt %, less than or equal to about 90 wt %,less than or equal to about 80 wt %, less than or equal to about 70 wt%, less than or equal to about 50 wt %, less than or equal to about 40wt %, less than or equal to about 20 wt %, less than or equal to about10 wt %, or less than or equal to about 5 wt %. Combinations of theabove-referenced ranges are also possible (e.g., a weight percentage ofgreater than about 5 wt % and less than or equal to about 90 wt %).Other ranges are also possible. In some embodiments, a fiber webincludes 0 wt % of hardwood fibers.

In embodiments in which the fiber web includes at least first and secondlayers, such as in the embodiment shown illustratively in FIG. 1, theweight percentage of hardwood fibers in each of the layers may alsovary. For example, in some embodiments, the weight percentage ofhardwood fibers in the first layer of the fiber web may be between about0 wt % and about 100 wt %. In some embodiments, the weight percentage ofhardwood fibers in the first layer of the fiber web may be greater thanor equal to about 10 wt %, greater than or equal to about 30 wt %,greater than or equal to about 50 wt %, greater than or equal to about70 wt %, or greater than or equal to about 80 wt %. In some embodiments,the weight percentage of hardwood fibers in the first layer of the fiberweb may be less than or equal to about 95 wt %, less than or equal toabout 90 wt %, less than or equal to about 80 wt %, less than or equalto about 70 wt %, less than or equal to about 50 wt %, or less than orequal to about 40 wt %, less than or equal to about 20 wt %, or lessthan or equal to about 10 wt %. Combinations of the above-referencedranges are also possible (e.g., a weight percentage of greater thanabout 5 wt % and less than or equal to about 80 wt %). Other ranges arealso possible.

In some embodiments, the weight percentage of hardwood fibers in thesecond layer of the fiber web may be between about 0 wt % and about 100wt %. In some embodiments, the weight percentage of hardwood fibers inthe second layer of the fiber web may be greater than or equal to about5 wt %, greater than or equal to about 10 wt %, greater than or equal toabout 30 wt %, greater than or equal to about 50 wt %, greater than orequal to about 70 wt %, or greater than or equal to about 80 wt %. Insome embodiments, the weight percentage of hardwood fibers in the secondlayer of the fiber web may be less than or equal to about 95 wt %, lessthan or equal to about 90 wt %, less than or equal to about 80 wt %,less than or equal to about 70 wt %, less than or equal to about 50 wt%, or less than or equal to about 40 wt %, less than or equal to about20 wt %, or less than or equal to about 10 wt %. Combinations of theabove-referenced ranges are also possible (e.g., a weight percentage ofgreater than about 5 wt % and less than or equal to about 80 wt %).Other ranges are also possible.

The weight percentage of softwood fibers in the fiber web may also vary.For example, the weight percentage of softwood fibers in the fiber webmay be between about 0 wt % and about 98 wt %. In some embodiments, theweight percentage of softwood fibers in the fiber web may be greaterthan or equal to about 5 wt %, greater than or equal to about 10 wt %,greater than or equal to about 30 wt %, greater than or equal to about50 wt %, greater than or equal to about 70 wt %, greater than or equalto about 80 wt %, greater than or equal to about 90 wt %, or greaterthan or equal to about 98 wt %. In some embodiments, the weightpercentage of the softwood fibers in the fiber web may be less than orequal to about 98 wt %, less than or equal to about 90 wt %, less thanor equal to about 80 wt %, less than or equal to about 70 wt %, lessthan or equal to about 50 wt %, less than or equal to about 40 wt %,less than or equal to about 20 wt %, less than or equal to about 10 wt%, or less than or equal to about 5 wt %. Combinations of theabove-referenced ranges are also possible (e.g., a weight percentage ofgreater than about 5 wt % and less than or equal to about 80 wt %).Other ranges are also possible. In some embodiments, a fiber webincludes 0 wt % of softwood fibers.

In embodiments in which the fiber web includes at least first and secondlayers, such as in the embodiment shown illustratively in FIG. 1, theweight percentage of softwood fibers in each of the layers may alsovary. For example, in some embodiments, the weight percentage ofsoftwood fibers in the first layer of the fiber web may be between about0 wt % and about 100 wt %. In some embodiments, the weight percentage ofsoftwood fibers in the first layer of the fiber web may be greater thanor equal to about 10 wt %, greater than or equal to about 30 wt %,greater than or equal to about 50 wt %, greater than or equal to about70 wt %, or greater than or equal to about 80 wt %. In some embodiments,the weight percentage of softwood fibers in the first layer of the fiberweb may be less than or equal to about 95 wt %, less than or equal toabout 90 wt %, less than or equal to about 80 wt %, less than or equalto about 70 wt %, less than or equal to about 50 wt %, or less than orequal to about 40 wt %, less than or equal to about 20 wt %, or lessthan or equal to about 10 wt %. Combinations of the above-referencedranges are also possible (e.g., a weight percentage of greater thanabout 5 wt % and less than or equal to about 80 wt %). Other ranges arealso possible.

In some embodiments, the weight percentage of softwood fibers in thesecond layer of the fiber web may be between about 0 wt % and about 100wt %. In some embodiments, the weight percentage of softwood fibers inthe second layer of the fiber web may be greater than or equal to about5 wt %, greater than or equal to about 10 wt %, greater than or equal toabout 30 wt %, greater than or equal to about 50 wt %, greater than orequal to about 70 wt %, or greater than or equal to about 80 wt %. Insome embodiments, the weight percentage of softwood fibers in the secondlayer of the fiber web may be less than or equal to about 95 wt %, lessthan or equal to about 90 wt %, less than or equal to about 80 wt %,less than or equal to about 70 wt %, less than or equal to about 50 wt%, or less than or equal to about 40 wt %, less than or equal to about20 wt %, or less than or equal to about 10 wt %. Combinations of theabove-referenced ranges are also possible (e.g., a weight percentage ofgreater than about 5 wt % and less than or equal to about 80 wt %).Other ranges are also possible.

In some embodiments, the fiber webs described herein include one or moresynthetic fibers. As described herein, the synthetic fibers may befibrillated or non-fibrillated. Synthetic fibers may include anysuitable type of synthetic polymer. Examples of suitable non-fibrillatedsynthetic fibers include polyesters (e.g., polyethylene terephthalate,polybutylene terephthalate), polyamide, polyaramid, para-aramid,meta-aramid, polyaniline, polyimide, polyethylene, polypropylene,polyether ether ketone, polyolefin, nylon, acrylics, polyvinyl alcohol,regenerated cellulose (e.g., lyocell, rayon), cellulose acetate,polyvinylidene fluoride, poly(vinylidenefluoride-co-hexafluoropropylene), polyacrylonitriles, polysulfones(e.g., polyether sulfones, poly(phenylene ether sulfone)), polystyrene,polybutadiene, polyurethane, polyphenylene oxide, polycarbonate,poly(methyl methacrylate), polyhydroxyethylmethacrylate, poly(lacticacid) or polylactide, silk, poly (4-methyl-1-pentene), polypyrrole, andcombinations thereof. In some embodiments, one or more fibers caninclude copolymers of the above (e.g., block copolymers ofpolystyrene-polybutadiene). In some embodiments, the synthetic fibersare organic polymer fibers.

Synthetic fibers may also include multi-component fibers (i.e., fibershaving multiple compositions such as bi-component fibers) including oneor more of the polymers described above. For example, islands in the seafibers may be used. In some cases, synthetic fibers may includemeltblown fibers, which may be formed of fibers described herein (e.g.,polyester, polypropylene). In other cases, synthetic fibers may beelectrospun fibers. In yet other embodiments, the synthetic fibers maybe centrifugal spun fibers or melt-spun fibers.

The fiber web, as well as the first and/or second layers of the fiberweb, may also include combinations of more than one type of syntheticfiber. It should be understood that other types of synthetic fiber typesmay also be used.

A fiber web may include a suitable percentage of synthetic fibers. Forexample, in some embodiments, the weight percentage of synthetic fibersin the fiber web may be between about 0 wt % and about 100 wt %. In someembodiments, the weight percentage of synthetic fibers in the fiber webmay be greater than or equal to about 5 wt %, greater than or equal toabout 10 wt %, greater than or equal to about 30 wt %, greater than orequal to about 50 wt %, greater than or equal to about 70 wt %, greaterthan or equal to about 80 wt %, greater than or equal to about 90 wt %,or greater than or equal to about 95 wt %. In some embodiments, theweight percentage of the synthetic fibers in the fiber web may be lessthan or equal to about 100 wt %, less than or equal to about 95 wt %,less than or equal to about 90 wt %, less than or equal to about 80 wt%, less than or equal to about 70 wt %, less than or equal to about 50wt %, less than or equal to about 40 wt %, less than or equal to about20 wt %, or less than or equal to about 10 wt %. Combinations of theabove-referenced ranges are also possible (e.g., a weight percentage ofgreater than about 50 wt % and less than or equal to about 100 wt %).Other ranges are also possible. In some embodiments, a fiber webincludes 100 wt % of synthetic fibers. In other embodiments, a fiber webincludes 0 wt % of synthetic fibers.

In certain embodiments, the fiber web includes one or more inorganicfibers. Inorganic fibers may include, for example, ceramic fibers suchas oxides (e.g., alumina, titania, tin oxide, zinc oxide). Mineralfibers can also be included in the fiber web. Inorganic fibers may alsoinclude metal fibers such as stainless steel fibers, nickel-coatedfibers, and copper-coated fibers.

In embodiments in which the fiber web includes at least first and secondlayers, such as in the embodiment shown illustratively in FIG. 1, theweight percentage of synthetic fibers in each of the layers may alsovary. For example, in some embodiments, the weight percentage ofsynthetic fibers in the first layer of the fiber web may be betweenabout 0 wt % and about 100 wt %. In some embodiments, the weightpercentage of synthetic fibers in the first layer of the fiber web maybe greater than or equal to about 10 wt %, greater than or equal toabout 30 wt %, greater than or equal to about 50 wt %, greater than orequal to about 70 wt %, or greater than or equal to about 80 wt %,greater than or equal to about 90 wt %, or greater than or equal toabout 95 wt %. In some embodiments, the weight percentage of syntheticfibers in the first layer of the fiber web may be less than or equal toabout 100 wt %, less than or equal to about 95 wt %, less than or equalto about 90 wt %, less than or equal to about 80 wt %, less than orequal to about 70 wt %, less than or equal to about 50 wt %, or lessthan or equal to about 40 wt %, less than or equal to about 20 wt %, orless than or equal to about 10 wt %. Combinations of theabove-referenced ranges are also possible (e.g., a weight percentage ofgreater than about 50 wt % and less than or equal to about 100 wt %).Other ranges are also possible. In some embodiments, the first layer ofthe fiber web includes 0 wt % of synthetic fibers. In other embodiments,the first layer of the fiber web includes 100 wt % of synthetic fibers.

In some embodiments, the weight percentage of synthetic fibers in thesecond layer of the fiber web may be between about 0 wt % and about 100wt %. In some embodiments, the weight percentage of synthetic fibers inthe second layer of the fiber web may be greater than or equal to about10 wt %, greater than or equal to about 30 wt %, greater than or equalto about 50 wt %, greater than or equal to about 70 wt %, or greaterthan or equal to about 80 wt %, greater than or equal to about 90 wt %,or greater than or equal to about 95 wt %. In some embodiments, theweight percentage of synthetic fibers in the second layer of the fiberweb may be less than or equal to about 100 wt %, less than or equal toabout 95 wt %, less than or equal to about 90 wt %, less than or equalto about 80 wt %, less than or equal to about 70 wt %, less than orequal to about 50 wt %, or less than or equal to about 40 wt %, lessthan or equal to about 20 wt %, or less than or equal to about 10 wt %.Combinations of the above-referenced ranges are also possible (e.g., aweight percentage of greater than about 50 wt % and less than or equalto about 100 wt %). Other ranges are also possible. In some embodiments,the second layer of the fiber web includes 100 wt % of synthetic fibers.

The fiber webs described herein may also include non-fibrillatedsynthetic fibers (e.g., staple fibers); that is, synthetic fibers thatare not fibrillated. Synthetic fibers, as noted above, are non-naturallyoccurring fibers formed of polymeric materials. Non-fibrillatedsynthetic fibers include any suitable type of synthetic polymerincluding thermoplastic polymers and those polymers described herein forsynthetic fibers generally. Examples of suitable non-fibrillatedsynthetic fibers include polyester, polyamide, polyaramid, polyimide,polyethylene, polypropylene, polyether ether ketone, polyethyleneterephthalate, polyolefin, nylon, and combinations thereof. It should beunderstood that other types of non-fibrillated synthetic fiber types mayalso be used.

In general, non-fibrillated synthetic fibers may have any suitabledimensions. For instance, non-fibrillated synthetic fibers may have anaverage diameter of between about 2 microns and about 50 microns,between about 2 microns and about 20 microns, between about 4 micronsand about 7 microns, or between about 3 microns and about 7 microns. Insome embodiments, the non-fibrillated synthetic fibers may have anaverage diameter of greater than or equal to about 1 micron, greaterthan or equal to about 2 microns, greater than or equal to about 4microns, greater than or equal to about 6 microns, greater than or equalto about 8 microns, greater than or equal to about 10 microns, greaterthan or equal to about 12 microns, greater than or equal to about 15microns, greater than or equal to about 20 microns, greater than orequal to about 30 microns, or greater than or equal to about 40 microns.In some cases, the non-fibrillated synthetic fibers may have an averagediameter of less than or equal to about 50 microns, less than or equalto about 40 microns, less than or equal to about 30 microns, less thanor equal to about 20 microns, less than or equal to about 15 microns,less than or equal to about 12 microns, less than or equal to about 10microns, than or equal to about 8 microns, less than or equal to about 6microns, less than equal to about 4 microns, or less than or equal toabout 2 microns. Combinations of the above referenced ranges are alsopossible (e.g., an average diameter of greater than or equal to about 2microns and less than about 10 microns). Other ranges are also possible.

In some embodiments, fiber webs having non-fibrillated synthetic fiberswith a greater average diameter may exhibit a higher degree ofpermeability than fiber webs having non-fibrillated synthetic fiberswith a comparatively smaller average diameter. The non-fibrillatedsynthetic fibers described may have an average length of between about 3mm and about 12 mm, between about 4 mm and about 6 mm, or between about5 mm and about 7 mm. In some embodiments, fiber webs havingnon-fibrillated synthetic fibers with a greater average length mayexhibit a higher degree of tensile strength than fiber webs havingnon-fibrillated synthetic fibers with a comparatively smaller averagelength. It should be understood that, in certain embodiments,non-fibrillated synthetic fibers may have dimensions outside theabove-noted ranges.

In some embodiments, non-fibrillated synthetic fibers may be staplefibers, which may be synthetic fibers that are cut or formed asnon-continuous discrete fibers to have a suitable average length and areappropriate for incorporation into a wet-laid or non-wet laid (e.g.,dry-laid, air laid) process for forming a fiber web. In some cases,groups of staple fibers may be cut to have a particular length with onlyslight variations in length between individual fibers.

In some embodiments, non-fibrillated synthetic fibers may be binderfibers. Non-fibrillated synthetic fibers may be mono-component (i.e.,having a single composition, such a polyvinyl alcohol or other polymersdescribed herein) or multi-component (i.e., having multiple compositionssuch as bi-component fiber). Combinations of different non-fibrillatedsynthetic fibers are also possible.

In some embodiments, the fiber web may include a suitable percentage ofmono-component fibers and/or multi-component fibers. In someembodiments, all of the non-fibrillated synthetic fibers aremono-component fibers. In some embodiments, at least a portion of thenon-fibrillated synthetic fibers are multi-component fibers.

An example of a multi-component fiber is a bi-component fiber whichincludes a first material and a second material that is different fromthe first material. The different components of a multi-component fibermay exhibit a variety of spatial arrangements. For example,multi-component fibers may be arranged in a core-sheath configuration(e.g., a first material may be a sheath material that surrounds a secondmaterial which is a core material), a side by side configuration (e.g.,a first material may be arranged adjacent to a second material), asegmented pie arrangement (e.g., different materials may be arrangedadjacent to one another in a wedged configuration), a tri-lobalarrangement (e.g., a tip of a lobe may have a material different fromthe lobe) and an arrangement of localized regions of one component in adifferent component (e.g., “islands in sea”).

In some embodiments, for a core-sheath configuration, a multi-componentfiber, such as a bi-component fiber, may include a sheath of a firstmaterial that surrounds a core comprising a second material. In such anarrangement, for some embodiments, the melting point of the firstmaterial may be lower than the melting point of the second material.Accordingly, at a suitable step during manufacture of a fiber web (e.g.,drying), the first material comprising the sheath may be melted (e.g.,may exhibit a phase change) while the second material comprising thecore remains unaltered (e.g., may exhibit no phase change). Forinstance, an outer sheath portion of a multi-component fiber may have amelting temperature between about 50° C. and about 200° C. (e.g., 180°C.) and an inner core of the multi-component fiber may have a meltingtemperature above 200° C. As a result, when the fiber is subjected to atemperature during drying, e.g., at 180° C., then the outer sheath ofthe fiber may melt while the core of the fiber does not melt.

A fiber web may include a suitable percentage of non-fibrillatedsynthetic fibers. For example, in some embodiments, the weightpercentage of non-fibrillated synthetic fibers in the fiber web may bebetween about 0 wt % and about 98 wt %. In some embodiments, the weightpercentage of non-fibrillated synthetic fibers in the fiber web may begreater than or equal to about 5 wt %, greater than or equal to about 10wt %, greater than or equal to about 30 wt %, greater than or equal toabout 50 wt %, greater than or equal to about 70 wt %, or greater thanor equal to about 80 wt %. In some embodiments, the weight percentage ofthe non-fibrillated synthetic fibers in the fiber web may be less thanor equal to about 95 wt %, less than or equal to about 90 wt %, lessthan or equal to about 80 wt %, less than or equal to about 70 wt %,less than or equal to about 50 wt %, less than or equal to about 40 wt%, less than or equal to about 20 wt %, or less than or equal to about10 wt %. Combinations of the above-referenced ranges are also possible(e.g., a weight percentage of greater than about 5 wt % and less than orequal to about 80 wt %). Other ranges are also possible. In someembodiments, a fiber web includes 0 wt % of non-fibrillated syntheticfibers.

In embodiments in which the fiber web includes at least first and secondlayers, such as in the embodiment shown illustratively in FIG. 1, theweight percentage of non-fibrillated synthetic fibers (e.g., staplefibers) in each of the layers may also vary. For example, in someembodiments, the weight percentage of non-fibrillated synthetic fibersin the first layer of the fiber web may be between about 0 wt % andabout 100 wt %. In some embodiments, the weight percentage ofnon-fibrillated synthetic fibers in the first layer of the fiber web maybe greater than or equal to about 10 wt %, greater than or equal toabout 30 wt %, greater than or equal to about 50 wt %, greater than orequal to about 70 wt %, or greater than or equal to about 80 wt %. Insome embodiments, the weight percentage of non-fibrillated syntheticfibers in the first layer of the fiber web may be less than or equal toabout 95 wt %, less than or equal to about 90 wt %, less than or equalto about 80 wt %, less than or equal to about 70 wt %, less than orequal to about 50 wt %, or less than or equal to about 40 wt %, lessthan or equal to about 20 wt %, or less than or equal to about 10 wt %.Combinations of the above-referenced ranges are also possible (e.g., aweight percentage of greater than about 5 wt % and less than or equal toabout 80 wt %). Other ranges are also possible. In some embodiments, thefirst layer of the fiber web includes 0 wt % of non-fibrillatedsynthetic fibers. In other embodiments, the first layer of the fiber webincludes 100 wt % of non-fibrillated synthetic fibers.

In some embodiments, the weight percentage of non-fibrillated syntheticfibers in the second layer of the fiber web may be between about 0 wt %and about 98 wt %. In some embodiments, the weight percentage ofnon-fibrillated synthetic fibers in the second layer of the fiber webmay be greater than or equal to about 10 wt %, greater than or equal toabout 30 wt %, greater than or equal to about 50 wt %, greater than orequal to about 70 wt %, or greater than or equal to about 80 wt %. Insome embodiments, the weight percentage of non-fibrillated syntheticfibers in the second layer of the fiber web may be less than or equal toabout 95 wt %, less than or equal to about 90 wt %, less than or equalto about 80 wt %, less than or equal to about 70 wt %, less than orequal to about 50 wt %, or less than or equal to about 40 wt %, lessthan or equal to about 20 wt %, or less than or equal to about 10 wt %.Combinations of the above-referenced ranges are also possible (e.g., aweight percentage of greater than about 5 wt % and less than or equal toabout 80 wt %). Other ranges are also possible. In some embodiments, thesecond layer of the fiber web includes 0 wt % of non-fibrillatedsynthetic fibers.

In some embodiments, the fiber web may include multiple types ofnon-fibrillated synthetic fibers.

The fiber web may include limited amounts of, if any, glass fibers. Forexample, the weight percentage of glass fiber in the fiber web may bebetween about 0 wt % and about 20 wt % (e.g., between about 0 wt % andabout 10 wt %, between 0 wt % and about 5 wt %, between 0 wt % and about2 wt %, or between 0 wt % and about 1 wt %). In some embodiments, theweight percentage of glass fibers in the fiber web may be less than orequal to about 20 wt %, less than or equal to about 15 wt %, less thanor equal to about 10 wt %, less than or equal to about 8 wt %, less thanor equal to about 6 wt %, less than or equal to about 5 wt %, less thanor equal to about 4 wt %, less than or equal to about 2 wt %, or lessthan or equal to about 1 wt %. Other ranges are also possible. When thefiber web includes less than 1 wt % of glass fiber, it is consideredthat the fiber web is substantially free of glass fiber.

In embodiments in which the fiber web includes at least first and secondlayers, such as in the embodiment shown illustratively in FIG. 1, theweight percentage of glass fibers in each of the layers may also vary.For example, in some embodiments, the weight percentage of glass fibersin the first layer of the fiber web may be between about 0 wt % andabout 20 wt % (e.g., between about 0 wt % to about 10 wt %, between 0 wt% to about 5 wt %, between 0 wt % to about 2 wt %, or between 0 wt % toabout 1 wt %). In some embodiments, the weight percentage of glassfibers in the first layer of the fiber web may be less than or equal toabout 20 wt %, less than or equal to about 15 wt %, less than or equalto about 10 wt %, less than or equal to about 8 wt %, less than or equalto about 6 wt %, less than or equal to about 5 wt %, less than or equalto about 4 wt %, less than or equal to about 2 wt %, or less than orequal to about 1 wt %. In some cases, the first layer includes 0 wt % ofglass fibers. Other ranges are also possible.

In some embodiments, the weight percentage of glass fibers in the secondlayer of the fiber web may be between about 0 wt % and about 20 wt %(e.g., between about 0 wt % to about 10 wt %, between 0 wt % to about 5wt %, between 0 wt % to about 2 wt %, or between 0 wt % to about 1 wt%). In some embodiments, the weight percentage of glass fibers in thesecond layer of the fiber web may be less than or equal to about 20 wt%, less than or equal to about 15 wt %, less than or equal to about 10wt %, less than or equal to about 8 wt %, less than or equal to about 6wt %, less than or equal to about 5 wt %, less than or equal to about 4wt %, less than or equal to about 2 wt %, or less than or equal to about1 wt %. In some cases, the second layer includes 0 wt % of glass fibers.Other ranges are also possible.

In some cases, a fiber web having limited amounts of, if any, glassfibers when used with various machine or engine parts may result in amarked decrease in abrasion and wear as compared to a fiber web havingsubstantially more glass fibers incorporated therein. Limited amounts orabsence of glass fibers may also reduce the amount of fiber sheddingfrom the fiber media during installation or use. Accordingly, usingfiber webs that include little to no glass fibers therein may alleviatethe necessity of having a protective scrim that may be otherwise beinstalled downstream from the filter media.

As described above, a fiber web may include an additional layer (e.g., athird layer, a fourth layer, . . . a tenth layer, etc.). The additionallayer may be positioned upstream or downstream of the first layer, orupstream or downstream of the second layer. In some cases, an additionallayer may be positioned between a first layer and a second layer.Moreover, more than one additional layers (e.g., up to 10 layers), whichmay be the same or different from one another, may be included in afiber web at various positions with respect to the first or secondlayers.

Although other ranges are possible, in certain embodiments theadditional layer may have a basis weight of between about 5 g/m² andabout 800 g/m², an air permeability of less than about 1300 cfm/sf, andan average fiber diameter of less than 100 microns. In some embodiments,the additional layer may be used to enhance one or more of dust holdingcapacity, lifetime, liquid filtration efficiency, water separationefficiency, and/or strength (e.g., Mullen burst strength, tensilestrength, elongation) of the fiber web, although other uses for theadditional layer are possible.

In some embodiments, an additional layer that may be used to enhancedust holding capacity of the fiber web may have, for example, a basisweight of less than or equal to 300 g/m², an air permeability of lessthan or equal to 700 cfm/sf, and an average fiber diameter of less thanor equal to 20 microns, although other ranges are also possible.

In some embodiments, an additional layer that may be used to enhanceefficiency of the fiber web may have, for example, a basis weight ofless than or equal to 100 g/m², an air permeability of less than orequal to 700 cfm/sf, and an average fiber diameter of less than or equalto 4 microns, although other ranges are also possible.

In some embodiments, an additional layer that may be used to enhancewater separation efficiency (e.g., fuel-water separation efficiency) ofthe fiber web may have, for example, a basis weight of less than orequal to 800 g/m², an air permeability of less than or equal to 1300cfm/sf, and an average fiber diameter of less than or equal to 50microns, although other ranges are also possible.

The additional layer may be formed of any suitable fibers and the layermay be non-woven or woven. In some cases, the additional layer isnon-wet laid and includes non-wet laid fibers, e.g., meltblown fibers,meltspun fibers, dry laid (carded) fibers, centrifugal spun fibers,spunbond fibers, and/or air laid fibers. In some cases, the additionallayer includes continuous fibers. In other cases, the additional layerincludes staple fibers (e.g., fibers having a length of between about 1mm and about 55 mm). In some embodiments, the additional layer does notinclude any fibrillated fibers, although fibrillated fibers may beincluded in other embodiments. The materials used to form the fibers ofthe additional layer may include the ones described herein (e.g.,synthetic, organic, and/or inorganic materials).

An additional layer may be in the form of a mesh in some cases. The meshmay be formed of any suitable materials such as the ones describedherein (e.g., synthetic, organic, and/or inorganic materials).Additionally, metals such as stainless steel may be used. The mesh mayhave an suitable average opening size, such as between about 0.001 mmand about 7 mm (e.g., at least about 0.001 mm, at least about 0.01 mm,at least about 0.1 mm, at least about 1 mm, at least about 3 mm, or atleast about 5 mm and/or less than or equal to about 7 mm, less than orequal to about 4 mm, less than or equal to about 2 mm, less than orequal to about 1 mm). Other ranges are also possible.

In general, the fibers of an additional layer may have any suitabledimensions. For instance, fibers of an additional layer may have anaverage diameter of between about 100 nm and about 100 microns (e.g.,between about 100 nm and about 50 microns, between about 100 nm andabout 4 microns, between about 1 micron and about 20 microns, or betweenabout 1 micron and about 50 microns). In some embodiments, theadditional layer may have an average diameter of greater than or equalto about 100 nm, greater than or equal to about 1 micron, greater thanor equal to about 2 microns, greater than or equal to about 4 microns,greater than or equal to about 10 microns, greater than or equal toabout 15 microns, greater than or equal to about 20 microns, greaterthan or equal to about 30 microns, or greater than or equal to about 40microns. In some cases, the fibers of an additional layer may have anaverage diameter of less than or equal to about 50 microns, less than orequal to about 40 microns, less than or equal to about 30 microns, lessthan or equal to about 20 microns, less than or equal to about 15microns, less than or equal to about 10 microns, less than or equal toabout 8 microns, less than or equal to about 6 microns, less than equalto about 4 microns, or less than or equal to about 2 microns, or lessthan or equal to about 1 micron. Combinations of the above referencedranges are also possible. Other ranges are also possible.

In some embodiments, the length of the fibers in an additional layer mayvary between about 1 mm and about 20 cm (e.g., at least about 1 mm, atleast about 5 mm, at least about 10 mm, at least about 50 mm, at leastabout 1 cm, at least about 5 cm, at least about 10 cm and/or less thanor equal to about 20 cm, less than or equal to about 15 cm, less than orequal to about 10 cm, less than or equal to about 5 cm, less than orequal to about 1 cm, less than or equal to about 50 mm, less than orequal to about 20 mm, or less than or equal to about 10 mm). Otherranges are also possible. Continuous fibers may also be included.

In one set of embodiments, a filter media includes a first layer and/ora second layer in combination with an additional layer described herein.The first layer and/or second layer may be a wet laid layer (e.g., alayer formed by a wet laid process). The additional layer may be anon-wet laid layer (e.g., it may include meltblown fibers, meltspunfibers, centrifugal spun fibers, electrospun fibers, or fibers formed byother non-wet laid processes). Generally, the first and/or second layerincludes a plurality of synthetic fibers and/or organic polymer fibers.For example, in one such embodiment, a filter media includes a firstlayer that comprises a plurality of organic polymer fibers, and a secondlayer that comprises a plurality of synthetic fibers. In someembodiments, at least one of the first and/or second layers includesfibrillated fibers in an amount described herein (e.g., between about 1wt % and about 100 wt % of the first and/or second layers).Additionally, the first and/or second layers may comprise between about0 wt % to about 10 wt % of glass fibers (e.g., the first and/or secondlayers may be substantially free of glass fibers). The first and/orsecond layers may be configured, in some embodiments, to have one ormore of the following: a [mean flow pore (μm)/(permeability(cfm/sf))^(0.5)] value of less than about 3.0; a dust holding capacityof greater than or equal to about 80 g/m²; and/or a liquid filtrationefficiency of at least 98% for 4 microns or greater particles. Theadditional layer, which may be used to enhance one or more of dustholding capacity, lifetime, liquid filtration efficiency, waterseparation efficiency, and/or strength (e.g., Mullen burst strength,tensile strength, elongation) of the fiber web, may include syntheticpolymer fibers. The additional layer may have, for example, a basisweight of between about 5 g/m² and about 800 g/m², an air permeabilityof less than about 100 cfm/sf, and an average fiber diameter of lessthan 100 microns. In some embodiments, the overall filter media may havean basis weight of greater than about 10 g/m² and less than or equal toabout 1000 g/m², a thickness of between about 0.1 mm and about 10.0 mm.Advantageously, in some embodiments involving a filter media including afirst layer, a second layer, and an additional layer, the filter mediacan achieve an efficiency at 4 microns of at least 99%, an initialefficiency of at least 99%, and a dust holding capacity of at least 150gsm. Other performance values are also possible. In some embodiments,the filter media can achieve a fuel-water separation efficiency of atleast about 30% (e.g., between about 60% to about 99.9%, between about80% to about 99.9%, or between about 90% to about 99.9%). In someembodiments, the fiber web may include a binder resin. The binder resinis not in fiber form and is to be distinguished from binder fiber (e.g.,multi-component fiber) described above. In general, the binder resin mayhave any suitable composition.

For example, the binder resin may comprise a thermoplastic (e.g.,acrylic, polyvinylacetate, polyester, polyamide), a thermoset (e.g.,epoxy, phenolic resin), or a combination thereof. In some cases, abinder resin includes one or more of a vinyl acetate resin, an epoxyresin, a polyester resin, a copolyester resin, a polyvinyl alcoholresin, an acrylic resin such as a styrene acrylic resin, and a phenolicresin. Other resins are also possible.

The amount of binder resin in a fiber web may vary. For example, theweight percentage of binder resin in the fiber web may be between 0 wt %and 45 wt %. In some embodiments, the weight percentage of binder resinin the fiber web may be greater than or equal to about 2 wt %, greaterthan or equal to about 5 wt %, greater than or equal to about 10 wt %,greater than or equal to about 15 wt %, greater than or equal to about20 wt %, greater than or equal to about 25 wt %, greater than or equalto about 30 wt %, greater than or equal to about 35 wt %, or greaterthan or equal to about 40 wt % In some cases, the weight percentage ofbinder resin in the fiber web may be less than or equal to about 45 wt%, less than or equal to about 40 wt %, less than or equal to about 35wt %, less than or equal to about 30 wt %, less than or equal to about25 wt %, less than or equal to about 20 wt %, less than or equal toabout 15 wt %, less than or equal to about 10 wt %, or less than orequal to about 5 wt %. Combinations of the above-referenced ranges arealso possible (e.g., a weight percentage of binder resin of greater thanor equal to about 5 wt % and less than about 35 wt %). Other ranges arealso possible.

As described further below, the binder resin may be added to the fibersin any suitable manner including, for example, in the wet fiber webstate. In some embodiments, the binder coats the fibers and is used toadhere fibers to each other to facilitate adhesion between the fibers.Any suitable method and equipment may be used to coat the fibers, forexample, using curtain coating, gravure coating, melt coating, dipcoating, knife roll coating, or spin coating, amongst others. In someembodiments, the binder is precipitated when added to the fiber blend.When appropriate, any suitable precipitating agent (e.g.,Epichlorhydrin, fluorocarbon) may be provided to the fibers, forexample, by injection into the blend. In some embodiments, upon additionto the fiber blend, the binder resin is added in a manner such that thefiber web is impregnated with the binder resin (e.g., the binder resinpermeates throughout the fiber web). In other embodiments, a binderresin may be added to one side or both sides of a layer or web after thelayer or web has been dried (e.g., after being formed using a wet laidprocess).

In a multi-layered web, a binder resin may be added to one or more, oreach of the layers separately prior to combining the layers, or thebinder resin may be added to the fiber web after combining the layers.In some embodiments, binder resin is added to the first and/or secondlayers, for example, by spraying or saturation impregnation (e.g., asolvent saturation process), or any of the above methods.

In some embodiments, a binder resin or binder mixture may be added tothe first and/or second layers of a fiber web by a solvent saturationprocess. In certain embodiments, a polymeric material can be impregnatedinto the first and/or second layers either during or after the layersare being manufactured on a papermaking machine. For example, during amanufacturing process described herein, after the article containingfirst layer and second layer is formed and dried, a polymeric materialin a water based emulsion or an organic solvent based solution can beadhered to an application roll and then applied to the article under acontrolled pressure by using a size press or gravure saturator. Theamount of the polymeric material impregnated into the article typicallydepends on the viscosity, solids content, and absorption rate ofarticle.

As another example, after a fiber web is formed, it can be impregnatedwith a polymeric material by using a reverse roll applicator followingthe just-mentioned method and/or by using a dip and squeeze method(e.g., by dipping a dried filter media into a polymer emulsion orsolution and then squeezing out the excess polymer by using a nip). Apolymeric material can also be applied to a fiber web by other methodsknown in the art, such as spraying or foaming.

It should be understood that the fiber web may, or may not, includeother components in addition to those described above. Typically, anyadditional components, are present in limited amounts, e.g., less than5% by weight. For example, in some embodiments, the fiber web mayinclude wet and dry strength additives or resins that include naturalpolymers (starches, gums), cellulose derivatives, such as carboxymethylcellulose, methylcellulose, hemicelluloses, synthetic polymers such asphenolics, latexes, polyamides, polyacrylamides, urea-formaldehyde,melamine-formaldehyde, polyamides), surfactants, coupling agents,crosslinking agents, and/or conductive additives, amongst others.

Fiber webs described herein may be used in an overall filtrationarrangement or filter element. In some embodiments, a fiber web includesat least a first layer and a second layer, with at least one of thelayers including a fibrillated fiber. In some embodiments, one or moreadditional layers or components are included with the fiber web (e.g.,disposed adjacent to the fiber web, contacting one or both sides of thefiber web). In some cases, the one or more additional layers may beformed predominantly of or entirely of non-fibrillated fibers, althoughin other embodiments, fibrillated fibers may be included. Non-limitingexamples of additional layers include a meltblown layer, a wet laidlayer, a coarse fiber electret media, a spunbond layer, or anelectrospun layer. In some embodiments, multiple fiber webs comprisingpredominantly fibrillated fibers and non-fibrillated fibers inaccordance with embodiments described herein may be layered together informing a multi-layer sheet for use in a filter media or element.

As described herein, in some embodiments two or more layers of a web maybe formed separately, and combined by any suitable method such aslamination, collation, or by use of adhesives. The two or more layersmay be formed using different processes, or the same process. Forexample, each of the layers may be independently formed by a wet laidprocess, a non-wet laid process (e.g., a dry laid process, a spinningprocess, a meltblown process), or any other suitable process. In certainembodiments, the wet laid layers or non-wet laid layers can be formed ona scrim or other suitable substrate directly.

In some embodiments, two or more layers may be formed by the sameprocess (e.g., a wet laid process, or a non-wet laid process such as adry laid process, a spinning process, a meltblown process, or any othersuitable process). In some instances, the two or more layers may beformed simultaneously. In some embodiments, a gradient in at least oneproperty may be present across the thickness of the two or more layers.

In embodiments in which a fiber web includes a meltblown layer, themeltblown layer may have one or more characteristics described incommonly-owned U.S. Patent Publication No. 2009/0120048, entitled“Meltblown Filter Medium”, which is based on U.S. patent applicationSer. No. 12/266,892, filed on May 14, 2009, and commonly-owned U.S.application Ser. No. 12/971,539, entitled “Fine Fiber Filter Media andProcesses”, filed on Dec. 17, 2010, each of which is incorporated hereinby reference in its entirety for all purposes.

Different layers may be adhered together by any suitable method. Forinstance, layers may be adhered by an adhesive and/or melt-bonded to oneanother on either side. Lamination and calendering processes may also beused. In some embodiments, an additional layer may be formed from anytype of fiber or blend of fibers via an added headbox or a coater andappropriately adhered to another layer.

The fiber webs (and resulting filter media) may have a variety ofdesirable properties and characteristics which are described in thefollowing paragraphs.

The basis weight of the fiber web can vary depending on factors such asthe strength requirements of a given filtering application, thematerials used to form the filter media, as well as the desired level offilter efficiency and permissible levels of resistance or pressure drop.In certain embodiments described herein, some fiber webs may have a lowbasis weight while achieving advantageous filtration performance ormechanical characteristics. For example, a fiber web incorporatingfibrillated fibers which provides for an enhanced surface area of thefiber web may have a lower basis weight without sacrificing strength.

The basis weight of the fiber web can typically be selected as desired.In some embodiments, the basis weight of the fiber web may range frombetween about 5 and about 1000 g/m². For instance, the basis weight ofthe fiber web may be between about 15 and about 400 g/m², between about30 and about 300 g/m², between about 50 and about 200 g/m², betweenabout 90 g/m² and about 200 g/m², between about 90 g/m² and about 150g/m². In some embodiments, the basis weight of the fiber web may begreater than or equal to about 5 g/m² (e.g., greater than or equal toabout 10 g/m², greater than or equal to about 40 g/m², greater than orequal to about 75 g/m², greater than or equal to about 100 g/m², greaterthan or equal to about 150 g/m², greater than or equal to about 200g/m², greater than or equal to about 250 g/m², greater than or equal toabout 300 g/m², greater than or equal to about 350 g/m², or greater thanor equal to about 400 g/m²). In some cases, the basis weight of thefiber web may be less than or equal to about 1000 g/m² (e.g., less thanor equal to about 700 g/m², less than or equal to about 500 g/m², lessthan or equal to about 400 g/m², less than or equal to about 350 g/m²,less than or equal to about 300 g/m², less than or equal to about 250g/m², less than or equal to about 200 g/m², less than or equal to about150 g/m², less than or equal to about 100 g/m², less than or equal toabout 75 g/m², or less than or equal to about 50 g/m²). Combinations ofthe above-referenced ranges are also possible (e.g., a basis weight ofgreater than about 40 g/m² and less than or equal to about 400 g/m²).Other ranges are also possible. As determined herein, the basis weightof the fiber web is measured according to the TAPPI T410Standard. Valuesare expressed in grams per square meter.

As described herein, in some embodiments a fiber web includes at leastfirst and second layers, as shown illustratively in FIG. 1. In some suchembodiments, the first layer may have a basis weight that ranges betweenabout 5 and about 1000 g/m². For instance, the basis weight of the firstlayer may be greater than or equal to about 8 g/m² (e.g., greater thanor equal to about 10 g/m², greater than or equal to about 40 g/m²,greater than or equal to about 65 g/m², greater than or equal to about75 g/m², greater than or equal to about 100 g/m², greater than or equalto about 150 g/m², greater than or equal to about 200 g/m², greater thanor equal to about 250 g/m², greater than or equal to about 300 g/m²,greater than or equal to about 350 g/m², greater than or equal to about400 g/m², greater than or equal to about 500 g/m², greater than or equalto about 600 g/m², greater than or equal to about 700 g/m², greater thanor equal to about 800 g/m², or greater than or equal to about 900 g/m²).In some cases, the basis weight of the first layer is less than or equalto about 1000 g/m² (e.g., less than or equal to about 1000 g/m², lessthan or equal to about 900 g/m², less than or equal to about 800 g/m²,less than or equal to about 700 g/m², less than or equal to about 600g/m², less than or equal to about 500 g/m², less than or equal to about400 g/m², less than or equal to about 350 g/m², less than or equal toabout 300 g/m², less than or equal to about 250 g/m², less than or equalto about 200 g/m², less than or equal to about 165 g/m², less than orequal to about 150 g/m², less than or equal to about 100 g/m², less thanor equal to about 75 g/m², less than or equal to about 50 g/m²).Combinations of the above-referenced ranges are also possible (e.g., afirst layer having a basis weight of greater than about 40 g/m² and lessthan or equal to about 350 g/m²). Other ranges are also possible.

The second layer may have a basis weight that ranges between about 3 andabout 1000 g/m². For instance, the basis weight of the second layer maybe greater than or equal to about 3 g/m² (e.g., greater than or equal toabout 8 g/m², greater than or equal to about 10 g/m², greater than orequal to about 15 g/m², greater than or equal to about 20 g/m², greaterthan or equal to about 30 g/m², greater than or equal to about 40 g/m²,greater than or equal to about 45 g/m², greater than or equal to about50 g/m², greater than or equal to about 75 g/m², greater than or equalto about 100 g/m², greater than or equal to about 150 g/m², greater thanor equal to about 200 g/m², greater than or equal to about 250 g/m²,greater than or equal to about 300 g/m², greater than or equal to about350 g/m², greater than or equal to about 400 g/m², greater than or equalto about 500 g/m², greater than or equal to about 600 g/m², greater thanor equal to about 700 g/m², greater than or equal to about 800 g/m², orgreater than or equal to about 900 g/m²). In some cases, the basisweight of the second layer is less than or equal to about 1000 g/m²,less than or equal to about 900 g/m², less than or equal to about 800g/m², less than or equal to about 700 g/m², less than or equal to about600 g/m², less than or equal to about 500 g/m², less than or equal toabout 400 g/m², less than or equal to about 350 g/m², less than or equalto about 300 g/m², less than or equal to about 250 g/m², less than orequal to about 200 g/m², less than or equal to about 165 g/m², less thanor equal to about 150 g/m², less than or equal to about 100 g/m², lessthan or equal to about 75 g/m² (e.g., less than or equal to about 50g/m², less than or equal to about 45 g/m², less than or equal to about40 g/m², less than or equal to about 35 g/m², less than or equal toabout 30 g/m², less than or equal to about 25 g/m², less than or equalto about 20 g/m², less than or equal to about 15 g/m², less than orequal to about 10 g/m², or less than or equal to about 5 g/m²).Combinations of the above-referenced ranges are also possible (e.g., asecond layer having a basis weight of greater than about 3 g/m² and lessthan or equal to about 50 g/m²). Other ranges are also possible.

In some embodiments, the basis weights of the first and second layersmay be chosen to achieve a particular basis weight ratio. For example,the basis weight ratio between the first and second layers (e.g., basisweight of first layer: basis weight of second layer) may be at least1:1, at least 2:1, at least 3:1, at least 5:1, at least 6:1, at least10:1, at least 15:1, or at least 20:1. In some embodiments, the basisweight ratio between the first and second layers is less than 20:1, lessthan 15:1, less than 14:1, less than 10:1, less than 6:1, less than 5:1,less than 4:1, less than 3:1, less than 2:1. Combinations of theabove-referenced ranges are also possible (e.g., a basis weight ratio ofat least 3:1 and less than 5:1). Other ranges are also possible.

In other embodiments, the basis weight ratio between the second andfirst layers (e.g., basis weight of second layer: basis weight of firstlayer) may be at least 1:1, at least 2:1, at least 3:1, at least 5:1, atleast 6:1, at least 10:1, at least 15:1, or at least 20:1. In someembodiments, the basis weight ratio between the first and second layersis less than 20:1, less than 15:1, less than 14:1, less than 10:1, lessthan 6:1, less than 5:1, less than 4:1, less than 3:1, less than 2:1.Combinations of the above-referenced ranges are also possible (e.g., abasis weight ratio of at least 3:1 and less than 5:1).

In embodiments in which an additional layer (e.g., a third layer, afourth layer, etc.) is included in a fiber web, the additional layer mayhave a basis weight that ranges between about 5 and about 800 g/m². Forinstance, the basis weight of the additional layer may be greater thanor equal to about 5 g/m² (e.g., greater than or equal to about 10 g/m²,greater than or equal to about 40 g/m², greater than or equal to about65 g/m², greater than or equal to about 75 g/m², greater than or equalto about 100 g/m², greater than or equal to about 150 g/m², greater thanor equal to about 200 g/m², greater than or equal to about 250 g/m²,greater than or equal to about 300 g/m², greater than or equal to about400 g/m², greater than or equal to about 500 g/m², greater than or equalto about 600 g/m², greater than or equal to about 700 g/m²). In somecases, the basis weight of the additional layer is less than or equal toabout 800 g/m² (e.g., less than or equal to about 700 g/m², less than orequal to about 600 g/m², less than or equal to about 500 g/m², less thanor equal to about 400 g/m², less than or equal to about 300 g/m², lessthan or equal to about 250 g/m², less than or equal to about 200 g/m²,less than or equal to about 165 g/m², less than or equal to about 150g/m², less than or equal to about 100 g/m², less than or equal to about75 g/m², less than or equal to about 50 g/m²). Combinations of theabove-referenced ranges are also possible (e.g., an additional layerhaving a basis weight of greater than about 5 g/m² and less than orequal to about 100 g/m²). Other ranges are also possible.

In certain embodiments, the fiber webs described herein may have arelatively high surface area. In certain embodiments, a fiber web mayhave a surface area between about 0.1 m²/g and about 100 m²/g. In somecases, a fiber web has a surface area of about 0.1 m²/g or greater,about 1 m²/g or greater, about 1.5 m²/g or greater, about 2.0 m²/g orgreater, about 2.5 m²/g or greater, about 3 m²/g or greater, about 5m²/g or greater, about 10 m²/g or greater, about 20 m²/g or greater,about 30 m²/g or greater, about 40 m²/g or greater, about 50 m²/g orgreater, about 60 m²/g or greater, about 70 m²/g or greater, about 80m²/g or greater, or about 90 m²/g or greater. In some embodiments, afiber web has a surface area of about 100 m²/g or less, about 90 m²/g orless, about 80 m²/g or less, about 70 m²/g or less, about 60 m²/g orless, about 50 m²/g or less, about 40 m²/g or less, about 30 m²/g orless, about 20 m²/g or less, about 10 m²/g or less, about 5 m²/g orless, or about 2 m²/g or less. Combinations of the above-referencedranges are also possible (e.g., a surface area of between about 100 m²/gor less and about 10 m²/g or greater). Other ranges are also possible.

In some embodiments, a layer (e.g., a first layer and/or a second layer)may have a surface area within one or more of the ranges describedabove.

As determined herein, surface area is measured through use of a standardBET surface area measurement technique. The BET surface area is measuredaccording to section 10 of Battery Council International StandardBCIS-03A, “Recommended Battery Materials Specifications Valve RegulatedRecombinant Batteries”, section 10 being “Standard Test Method forSurface Area of Recombinant Battery Separator Mat”. Following thistechnique, the BET surface area is measured via adsorption analysisusing a BET surface analyzer (e.g., Micromeritics Gemini III 2375Surface Area Analyzer) with nitrogen gas; the sample amount is between0.5 and 0.6 grams in a ¾″ tube; and, the sample is allowed to degas at75 degrees C. for a minimum of 3 hours.

Thickness, as referred to herein, is determined according to theStandard TAPPI T411. The thickness of the fiber web may be between about0.3 mm and about 10 mm. In some embodiments, the thickness of the fiberweb may be greater than or equal to about 0.3 mm, greater than or equalto about 0.5 mm, greater than or equal to about 0.6 mm, greater than orequal to about 0.8 mm, greater than or equal to about 1.0 mm, greaterthan or equal to about 1.2 mm, greater than or equal to about 1.5 mm,greater than or equal to about 2 mm, greater than or equal to about 3mm, greater than or equal to about 4 mm, greater than or equal to about5 mm, or greater than or equal to about 7 mm. In certain embodiments,the thickness of the fiber web may be less than or equal to about 10 mm,less than or equal to about 7 mm, less than or equal to about 5 mm, lessthan or equal to about 4 mm, less than or equal to about 2 mm, less thanor equal to about 1.2 mm, less than or equal to about 1.0 mm, less thanor equal to about 0.8 mm, less than or equal to about 0.6 mm, or lessthan or equal to about 0.4 mm, less than or equal to about 0.2 mm.Combinations of the above-referenced ranges are also possible (e.g., athickness of greater than about 0.3 mm and less than or equal to about1.0 mm). Other ranges are also possible.

In some embodiments, a layer (e.g., a first layer and/or a second layer)may have a thickness within one or more of the ranges described abovefor the entire fiber web.

The fiber web may exhibit a suitable mean flow pore size. Mean flow poresize, as determined herein, is measured according to Standard ASTM F316.In some embodiments, the mean flow pore size may range between about 0.1microns and about 50 microns (e.g., between about 0.1 microns and about5 microns, between about 5 microns and about 40 microns, between about15 microns and about 40 microns, or between about 25 microns and about40 microns). In some embodiments, the mean flow pore size of the fiberweb may be less than or equal to about 50 microns, less than or equal toabout 45 microns, less than or equal to about 40 microns, less than orequal to about 30 microns, less than or equal to about 25 microns, lessthan or equal to about 20 microns, less than or equal to about 15microns, less than or equal to about 10 microns, or less than or equalto about 5 microns, less than or equal to about 3 microns, less than orequal to about 2 microns, less than or equal to about 1 micron, lessthan or equal to about 0.8 microns, less than or equal to about 0.5microns, or less than or equal to about 0.2 microns. In otherembodiments, the mean flow pore size may be greater than or equal toabout 0.1 microns, greater than or equal to about 0.2 microns, greaterthan or equal to about 0.5 microns, greater than or equal to about 0.8microns, greater than or equal to about 1 micron, greater than or equalto about 2 microns, greater than or equal to about 5 microns, greaterthan or equal to about 10 microns, greater than or equal to about 15microns, greater than or equal to about 20 microns, greater than orequal to about 25 microns, greater than or equal to about 30 microns,greater than or equal to about 35 microns, greater than or equal toabout 45 microns or greater than or equal to about 50 microns.Combinations of the above-referenced ranges are also possible (e.g., amean flow pore size of greater than or equal to about 10 microns andless than or equal to about 50 microns). Other values and ranges of meanflow pore size are also possible.

In some embodiments, it may be preferable for the fiber web to exhibitcertain mechanical properties. For example, as described above, a fiberweb comprised primarily of fibrillated synthetic fibers andnon-fibrillated synthetic fibers (e.g., a fiber web having limitedamounts of, or no, glass fiber) may give rise to a relatively flexibleand strong filter media that does not include with it the environmentalissues associated with conventional glass fibers in the filter media. Insome embodiments, fiber webs described herein that have little to noglass fibers may exhibit a greater degree of elongation, burst strengthand/or tensile strength relative to fiber webs having comparatively moreglass fibers incorporated therein.

In some embodiments, the tensile elongation in the machine direction ofthe fiber web may be greater than about 0.2%, greater than about 0.5%,greater than about 0.8%, greater than about 2%, greater than about 5%,greater than about 8%, greater than about 10%, and/or less than or equalto about 12%. For example, the tensile elongation in the machinedirection of the fiber web may be between about 0.2% and about 4.0%,between about 0.2% and about 3.0%, between about 0.5% and about 3.5%,between about 0.5% and about 2.0%, between about 1.0% and about 3.0%,between about 1.5% and about 2.5%, or between about 0.2% and about 12%.In some embodiments, the tensile elongation in the cross-machinedirection of the fiber web may be greater than about 0.2%, greater thanabout 0.5%, greater than about 0.8%, or greater than about 1.0%, greaterthan about 2%, greater than about 5%, greater than about 8%, greaterthan about 10%, and/or less than or equal to about 12%. For example, thetensile elongation in the cross-machine direction of the fiber web maybe between about 0.2% and about 6.0%, between about 0.2% and about 5.0%,between about 0.2% and about 4.0%, between about 0.5% and about 4.5%,between about 1.0% and about 3.5%, between about 1.0% and about 3.0%,between about 2.0% and about 3.5%, or between about 0.2% and about 12%.In some cases, fiber webs that exhibit an increased degree of elongationmay also be more pleatable, for example, by exhibiting an overallreduction in potential damage that may arise at the edges of the filtermedia.

The tensile strength in the machine direction of the filter media may begreater than about 2 N/15 mm, greater than about 4 N/15 mm, greater thanabout 6 N/15 mm, greater than about 10 N/15 mm, greater than about 20N/15 mm, greater than about 50 N/15 mm, greater than about 75 N/15 mm,greater than about 100 N/15 mm, greater than about 125 N/15 mm, greaterthan about 150 N/15 mm, or greater than about 175 N/15 mm, and/or lessthan or equal to about 200 N/15 mm. For example, the tensile strength inthe machine direction of the fiber web may be between about 3 N/15 mmand about 20 N/15 mm, between about 1 N/15 mm and about 6 N/15 mm,between about 10 N/15 mm and about 20 N/15 mm, between about 1 N/15 mmand about 200 N/15 mm, or between about 100 N/15 mm and about 200 N/15mm. The tensile strength of the fiber web in the cross-machine directionmay be greater than about 1 N/15 mm, greater than about 3 N/15 mm,greater than about 4 N/15 mm, greater than about 6 N/15 mm, greater thanabout 10 N/15 mm, greater than about 20 N/15 mm, greater than about 50N/15 mm, greater than about 75 N/15 mm, greater than about 100 N/15 mm,greater than about 125 N/15 mm, greater than about 150 N/15 mm, orgreater than about 175 N/15 mm, and/or less than or equal to about 200N/15 mm. In some cases, the tensile strength of the fiber web in thecross-machine direction may be between about 1 N/15 mm and about 6 N/15mm, between about 2 N/15 mm and about 10 N/15 mm, or between about 3N/15 mm and about 9 N/15 mm, between about 1 N/15 mm and about 200 N/15mm, or between about 100 N/15 mm and about 200 N/15 mm. In some cases,the cross machine direction tensile strength may be greater or less thanthe machine direction tensile strength.

Tensile strength and tensile elongation are measured according to theStandard TAPPI T494.

Mullen burst tests may be used as a further test for strength inmeasuring the pressure required for puncturing the fiber web as anindicator of the load carrying capacity of the fiber web under certainconditions. Mullen burst strength is measured according to the StandardTAPPI T403. In some embodiments, the Mullen burst strength for the fiberweb may be greater than 10 psi, greater than 15 psi, greater than 30psi, greater than 40 psi, greater than 60 psi, greater than 75 psi, orbetween about 5 psi and about 120 psi, between about 5 psi and about 50psi, or between about 30 psi and about 100 psi.

The fiber web described herein may also exhibit advantageous filtrationperformance characteristics, such as dust holding capacity (DHC),efficiency, air permeability, amongst others.

The fiber webs described herein can have beneficial dust holdingproperties. In some embodiments, the fiber web may have a DHC of betweenabout 80 g/m² and about 300 g/m². In some embodiments, the DHC may begreater than or equal to about 80 g/m², greater than or equal to about100 g/m², greater than or equal to about 125 g/m², greater than or equalto about 150 g/m², greater than or equal to about 175 g/m², greater thanor equal to about 200 g/m², greater than or equal to about 225 g/m²,greater than or equal to about 250 g/m², greater than or equal to about275 g/m², greater than or equal to about 300 g/m², or greater than orequal to about 350 g/m². In some cases, the DHC may be less than orequal to about 400 g/m², less than or equal to about 350 g/m², less thanor equal to about 300 g/m², less than or equal to about 275 g/m², lessthan or equal to about 250 g/m², less than or equal to about 225 g/m²,less than or equal to about 200 g/m², less than or equal to about 175g/m², less than or equal to about 150 g/m², less than or equal to about125 g/m², or less than or equal to about 100 g/m². Combinations of theabove-referenced ranges are also possible (e.g., a DHC of greater thanabout 150 g/m² and less than or equal to about 300 g/m²). Other rangesare also possible.

The dust holding capacity, as referred to herein, is tested based on aMultipass Filter Test following the ISO 16889/19438 procedure (modifiedby testing a flat sheet sample) on a Multipass Filter Test Standmanufactured by FTI. The test may be run under different conditions. Thetesting uses ISO A3 Medium test dust manufactured by PTI, Inc. at a baseupstream gravimetric dust level (BUGL) of 10 to 50 mg/liter. The testfluid is Aviation Hydraulic Fluid AERO HFA MIL H-5606A manufactured byMobil. The test is run at a face velocity of 0.06 to 0.16 cm/s until aterminal pressure of 1 to 2 (100 to 200 kPa). Unless otherwise stated,the dust holding capacity values (and/or efficiency values) describedherein are determined at a BUGL of 25 mg/L, a face velocity of 0.06cm/s, and a terminal pressure of 100 kPa.

The efficiency (e.g., liquid filtration efficiency) and initialefficiency (e.g., initial liquid filtration efficiency) of filteringvarious particle sizes can be measured using the Multipass Filter Testdescribed above. Suitable fiber webs may be used for the filtration ofparticles having a size, for example, of greater than or equal to about50 microns, greater than or equal to about 30 microns, greater than orequal to about 20 microns, greater than or equal to about 15 microns,greater than or equal to about 10 microns, greater than or equal toabout 5 microns, greater than or equal to about 4 microns, greater thanor equal to about 3 microns, or greater than or equal to about 1 micron.Particle counts (particles per milliliter) at the minimum particle size,x, selected (e.g., where x is 1, 2, 3, 4, 5, 7, 10, 15, 20, 25, 30, 40or 50 microns) upstream and downstream of the media can be taken at tenpoints equally divided over the time of the test. Generally, a particlesize of x means that x micron or greater particles will be captured bythe layer or media. The average of upstream and downstream particlecounts can be taken at each selected minimum particle size and particlesgreater than that size. From the average particle count upstream(injected, C₀) and the average particle count downstream (passed thru,C), the liquid filtration efficiency test value for each minimumparticle size selected can be determined by the relationship[(1−[C/C₀])*100%]. As described herein, efficiency can be measuredaccording to standard ISO 16889/19438 procedure. A similar protocol canbe used for measuring initial efficiency, which refers to the averageefficiency measurements of the media at 4, 5, and 6 minutes afterrunning the test. Unless otherwise indicated, efficiency and initialefficiency measurements described herein refer to values where x=4microns.

The fiber webs described herein may have a wide range of efficiencies(e.g., liquid filtration efficiencies). In some embodiments, a fiber webhas an efficiency of between about 90% and about 100%. The efficiencymay be, for example, greater than or equal to about 90%, greater than orequal to about 92%, greater than or equal to about 94%, greater than orequal to about 96%, greater than or equal to about 98%, greater than orequal to about 99%, greater than or equal to about 99.4%, greater thanor equal to about 99.5%, greater than or equal to about 99.7%, greaterthan or equal to about 99.8%, greater than or equal to about 99.9%, orgreater than or equal to about 99.99%. Such efficiencies may be achievedfor filtering particles of different sizes such as particles of 10microns or greater, particles of 8 microns or greater, particles of 6microns or greater, particles of 5 microns or greater, particles of 4microns or greater, particles of 3 microns or greater, particles of 2microns or greater, or particles of 1 micron or greater. Other particlesizes and efficiencies are also possible.

Efficiency values described above are applicable for single layerarrangements as well as for arrangements that include multilayers. Forexample, the combined filtration arrangement including a first layer anda second layer, wherein one of the layers includes at least onefibrillated fiber, may exhibit an efficiency of greater than or equal toabout 90%, greater than or equal to about 92%, greater than or equal toabout 94%, greater than or equal to about 96%, greater than or equal toabout 98%, greater than or equal to about 99%, greater than or equal toabout 99.4%, greater than or equal to about 99.5%, greater than or equalto about 99.7%, greater than or equal to about 99.8%, greater than orequal to about 99.9%, or greater than or equal to about 99.99% forparticles of 4 microns or greater in some embodiments, particles of 3microns or greater in other embodiments, particles of 2 microns orgreater in yet other embodiments, or particles of 1 micron or greater infurther embodiments.

In some embodiments, a layer (e.g., a first layer, a second layer,and/or an additional layer) may have an efficiency within one or more ofthe ranges described above.

Additionally, a fiber web may have a suitable initial efficiency. Insome embodiments, the initial efficiency may range from about 30% toabout 99.999% (e.g., between about 60% to about 99.9%). For instance, incertain embodiments, the initial efficiency may be at least about 30%,at least about 40%, at least about 50%, at least about 60%, at leastabout 70%, at least about 80%, at least about 90%, at least about 95%,at least about 98%, at least about 99%, at least about 99.9%. Otherranges are also possible.

In some embodiments, a layer (e.g., a first layer, a second layer and/oran additional layer) may have an initial efficiency within one or moreof the ranges described above.

In certain embodiments, a fiber web may be configured to achieve a highfuel-water separation efficiency, e.g., for separating out water from afuel-water emulsion. In some embodiments, the fuel-water separationefficiency may range from about 30% to about 99.999% (e.g., betweenabout 60% to about 99.9%). For instance, in certain embodiments, thefuel-water separation efficiency may be at least about 30%, at leastabout 40%, at least about 50%, at least about 60%, at least about 70%,at least about 80%, at least about 90%, at least about 95%, at leastabout 98%, at least about 99%, at least about 99.9%. Other ranges arealso possible.

As used herein, a fuel-water separation efficiency is measured using theSAEJ1488 test. The test involves sending a fuel (ultra-low sulfur dieselfuel) with a controlled water content (2500 ppm) through a pump acrossthe media at a face velocity of 0.069 cm/sec. The water is emulsifiedinto fine droplets and sent to challenge the media. The water is eithercoalesced, or shed or both, and collects at the bottom of the housing.The water content is measured both upstream and downstream of the media,via Karl Fischer titration. The efficiency is the amount of waterremoved from the fuel-water mixture. The fuel-water separationefficiency is calculated as (1−C/2500)*100, where C is the downstreamconcentration of water.

Generally, the media can be classified as coalescing or shedding basedon the amount of water collected. If the water collection is moreupstream, then the media is primarily shedding. If the water collectingis more down-stream, then the media is primarily coalescing.Combinations can also occur where the media can be both coalescing andshedding.

The fiber webs may exhibit suitable air permeability characteristics. Insome embodiments, the air permeability may range from between about 0.1cubic feet per minute per square foot (cfm/sf) and about 250 cfm/sf(e.g., between about 0.5 cfm/sf and about 50 cfm/sf, between about 50cfm/sf and about 125 cfm/sf, between about 5 cfm/sf and about 150cfm/sf, between about 10 cfm/sf and about 150 cfm/sf, or between about50 cfm/sf and about 150 cfm/sf). In some embodiments, the airpermeability may be greater than or equal to about 0.5 cfm/sf, greaterthan or equal to about 2 cfm/sf, greater than or equal to about 5cfm/sf, greater than or equal to about 10 cfm/sf, greater than or equalto about 25 cfm/sf, greater than or equal to about 50 cfm/sf, greaterthan or equal to about 75 cfm/sf, greater than or equal to about 100cfm/sf, greater than or equal to about 150 cfm/sf, greater than or equalto about 200 cfm/sf, or greater than or equal to about 250 cfm/sf. Incertain embodiments, the air permeability may be less than or equal toabout 250 cfm/sf, less than or equal to about 200 cfm/sf, less than orequal to about 175 cfm/sf, less than or equal to about 150 cfm/sf, lessthan or equal to about 125 cfm/sf, less than or equal to about 100cfm/sf, less than or equal to about 75 cfm/sf, less than or equal toabout 50 cfm/sf, less than or equal to about 25 cfm/sf, or less than orequal to about 5 cfm/sf. Combinations of the above-referenced ranges arealso possible (e.g., an air permeability of greater than or equal to 5cfm/sf and less than or equal to about 200 cfm/sf). Other ranges arealso possible.

As determined herein, the permeability is measured according to theStandard TAPPI T-251. The permeability is an inverse function of flowresistance and can be measured with a Frazier Permeability Tester (e.g.,TexTest Instrument, FX 3300). The Frazier Permeability Tester measuresthe volume of air per unit of time that passes through a unit area ofsample at a fixed differential pressure across the sample. Permeabilitycan be expressed in cubic feet per minute per square foot at a 0.5 inchwater differential.

In some embodiments, a layer (e.g., a first layer and/or a second layer)may have a permeability within one or more of the ranges describedabove.

In some embodiments, an additional layer (e.g., a third layer, a fourthlayer, etc.) of the fiber web may have an air permeability between about0.5 cubic feet per minute per square foot (cfm/sf) and about 1500 cfm/sf(e.g., between about 0.5 cfm/sf and about 70 cfm/sf, between about 5cfm/sf and about 700 cfm/sf, or between about 5 cfm/sf and about 1300cfm/sf). In some embodiments, the air permeability may be greater thanor equal to about 0.5 cfm/sf, greater than or equal to about 5 cfm/sf,greater than or equal to about 10 cfm/sf, greater than or equal to about50 cfm/sf, greater than or equal to about 70 cfm/sf, greater than orequal to about 100 cfm/sf, greater than or equal to about 300 cfm/sf,greater than or equal to about 500 cfm/sf, greater than or equal toabout 700 cfm/sf, or greater than or equal to about 1000 cfm/sf. Incertain embodiments, the air permeability may be less than or equal toabout 1500 cfm/sf, less than or equal to about 1300 cfm/sf, less than orequal to about 1000 cfm/sf, less than or equal to about 800 cfm/sf, lessthan or equal to about 400 cfm/sf, less than or equal to about 100cfm/sf, or less than or equal to about 50 cfm/sf. Combinations of theabove-referenced ranges are also possible. Other ranges are alsopossible.

In some embodiments, the fiber webs described herein may have a certainrelationship between mean flow pore size to permeability. Therelationship between mean flow pore size and permeability may beexpressed as [mean flow pore (μm)/(permeability (cfm/sf))^(0.5)], alsoreferred to herein as the Perm. Pore Index. In other words, the meanflow pore size of the fiber media may be divided by the square root ofthe permeability of the media. Generally, a fiber web having a higherefficiency may have a lower [mean flow pore (μm)/(permeability(cfm/sf)^(0.5)] value if all other factors are equal.

In some embodiments, the fiber webs described herein have a [mean flowpore (μm)/(permeability (cfm/sf))^(0.5)] value of between about 0.5 andabout 3.0. In some embodiments, a fiber web has a [mean flow pore(μm)/(permeability (cfm/sf))^(0.5)] value of less than or equal to about3, less than or equal to about 2.5, less than or equal to about 2, lessthan or equal to about 1.8, less than or equal to about 1.6, less thanor equal to about 1.5, less than or equal to about 1.4, less than orequal to about 1.2, less than or equal to about 1.0, less than or equalto about 0.9, less than or equal to about 0.8, less than or equal toabout 0.7, or less than or equal to about 0.6. In some embodiments, afiber web has a [mean flow pore (μm)/(permeability (cfm/sf))^(0.5)]value of greater than or equal to about 0.5, greater than or equal toabout 0.6, greater than or equal to about 0.8, greater than or equal toabout 1.0, greater than or equal to about 1.2, greater than or equal toabout 1.5, or greater than or equal to about 2.0. Combinations of theabove-referenced ranges are also possible (e.g., a [mean flow pore(μm)/(permeability (cfm/sf)^(0.5)] value of greater than about 0.5 andless than or equal to about 1.5). Other values are also possible.

In some embodiments, a layer (e.g., a first layer and/or a second layer)may have a [mean flow pore (μm)/(permeability (cfm/sf))^(0.5)] valuewithin one or more of the ranges described above.

It should be appreciated that although the parameters andcharacteristics noted above are described with respect to fiber webs,the same parameters and characteristics (including the values and rangesfor such parameters and characteristics) may also be applied to filtermedia.

Fiber webs described herein may be produced using suitable processes,such as using a wet laid process or a non-wet laid process (e.g., a drylaid process, a spinning process, a meltblown process, or any othersuitable process). In general, a wet laid process involves mixingtogether of fibers of one or more type; for example, non-fibrillatedfibers (e.g., mono-component and/or bi-component fibers) may be mixedtogether with fibrillated fibers, or any other components (e.g., othertypes of synthetic fibers), to provide a fiber slurry. In certainembodiments, only fibrillated fibers are included in a slurry. In someembodiments, the fibrillated fibers are of one type but have differentlevels of fibrillation. The slurry may be, for example, an aqueous-basedslurry. In certain embodiments, fibrillated fibers, optionalnon-fibrillated fibers, and any other appropriate fibers, are optionallystored separately, or in combination, in various holding tanks prior tobeing mixed together (e.g., to achieve a greater degree of uniformity inthe mixture).

For instance, a first fiber (e.g., fibrillated fibers or non-fibrillatedfibers) may be mixed and pulped together in one container and a secondfiber (e.g., fibrillated fibers) may be mixed and pulped in a separatecontainer. The first fibers and the second fibers may subsequently becombined together into a single fibrous mixture. Appropriate fibers maybe processed through a pulper before and/or after being mixed together.In some embodiments, combinations of fibers such as non-fibrillatedfibers, fibrillated fibers and/or other synthetic fibers, are processedthrough a pulper and/or a holding tank prior to being mixed together. Itcan be appreciated that other components may also be introduced into themixture. Furthermore, it should be appreciated that other combinationsof fibers types may be used in fiber mixtures, such as the fiber typesdescribed herein.

In certain embodiments, two or more layers are formed by a wet laidprocess. For example, a first dispersion (e.g., a pulp) containingfibers in a solvent (e.g., an aqueous solvent such as water) can beapplied onto a wire conveyor in a papermaking machine (e.g., afourdrinier or a rotoformer) to form first layer supported by the wireconveyor. A second dispersion (e.g., another pulp) containing fibers ina solvent (e.g., an aqueous solvent such as water) is applied onto thefirst layer either at the same time or subsequent to deposition of thefirst layer on the wire. Vacuum is continuously applied to the first andsecond dispersions of fibers during the above process to remove thesolvent from the fibers, thereby resulting in an article containingfirst and second layers. The article thus formed is then dried and, ifnecessary, further processed (e.g., calendered) by using known methodsto form multi-layered fiber webs. In some embodiments, such a processmay result in a gradient in at least one property across the thicknessof the two or more layers.

Any suitable method for creating a fiber slurry may be used. In someembodiments, further additives are added to the slurry to facilitateprocessing. The temperature may also be adjusted to a suitable range,for example, between 33° F. and 100° F. (e.g., between 50° F. and 85°F.). In some cases, the temperature of the slurry is maintained. In someinstances, the temperature is not actively adjusted.

In some embodiments, the wet laid process uses similar equipment as in aconventional papermaking process, for example, a hydropulper, a formeror a headbox, a dryer, and an optional converter. A fiber web can alsobe made with a laboratory handsheet mold in some instances. As discussedabove, the slurry may be prepared in one or more pulpers. Afterappropriately mixing the slurry in a pulper, the slurry may be pumpedinto a headbox where the slurry may or may not be combined with otherslurries. Other additives may or may not be added. The slurry may alsobe diluted with additional water such that the final concentration offiber is in a suitable range, such as for example, between about 0.1% to0.5% by weight.

Wet laid processes may be particularly suitable for forming gradients ofone or more properties in a fiber web, such as those described herein.For instance, in some cases, the same slurry is pumped into separateheadboxes to form different layers and/or a gradient in a fiber web. Inother cases, two or more different slurries may be pumped into separateheadboxes to form different layers and/or a gradient in a fiber web. Forlaboratory samples, a first layer can be formed from a fiber slurry,drained and dried and then a second layer can be formed on top from afiber slurry. In other embodiments, a first layer can be formed and asecond layer can be formed on top, drained and dried.

In some cases, the pH of the fiber slurry may be adjusted as desired.For instance, fibers of the slurry may be dispersed under generallyneutral conditions.

Before the slurry is sent to a headbox, the slurry may optionally bepassed through centrifugal cleaners and/or pressure screens for removingunfiberized material. The slurry may or may not be passed throughadditional equipment such as refiners or deflakers to further enhancethe dispersion or fibrillation of the fibers. For example, deflakers maybe useful to smooth out or remove lumps or protrusions that may arise atany point during formation of the fiber slurry. Fibers may then becollected on to a screen or wire at an appropriate rate using anysuitable equipment, e.g., a fourdrinier, a rotoformer, a cylinder, or aninclined wire fourdrinier.

In some embodiments, the process involves introducing binder (and/orother components) into a pre-formed fiber layer (e.g., including afibrillated fiber with a non-fibrillated fiber). In some embodiments, asthe fiber layer is passed along an appropriate screen or wire, differentcomponents included in the binder, which may be in the form of separateemulsions, are added to the fiber layer using a suitable technique. Insome cases, each component of the binder resin is mixed as an emulsionprior to being combined with the other components and/or fiber layer. Insome embodiments, the components included in the binder may be pulledthrough the fiber layer using, for example, gravity and/or vacuum. Insome embodiments, one or more of the components included in the binderresin may be diluted with softened water and pumped into the fiberlayer. In some embodiments, a binder may be introduced to the fiberlayer by spraying onto the formed media, or by any other suitablemethod, such as for example, size press application, foam saturation,curtain coating, rod coating, amongst others. In some embodiments, abinder material may be applied to a fiber slurry prior to introducingthe slurry into a headbox. For example, the binder material may beintroduced (e.g., injected) into the fiber slurry and impregnated withand/or precipitated on to the fibers. In some embodiments, a binderresin may be added to a fiber web by a solvent saturation process, asdescribed in more detail herein.

In other embodiments, a non-wet laid process is used to form one or morelayers of a fiber web. In certain embodiments, a non-wet laid processinvolves a dry laid process, such as a carding process. In someembodiments, an air laid process is used. For example, in an air laidprocess, non-fibrillated synthetic fibers may be mixed along withfibrillated fibers (e.g., lyocell) while air is blown onto a conveyor,and a binder is then applied. In a carding process, in some embodiments,the fibers are manipulated by rollers and extensions (e.g., hooks,needles) associated with the rollers prior to application of the binder.In some cases, forming the fiber webs through a non-wet laid process maybe more suitable for the production of a highly porous media.

As described herein, a first and/or second layer of a fiber web may beformed by a non-wet laid process. In some embodiments, the first and/orsecond layer may be impregnated (e.g., via saturation, spraying, etc.)with any suitable binder resin, as discussed above.

During or after formation of a fiber web, the fiber web may be furtherprocessed according to a variety of known techniques. Optionally,additional layers can be formed and/or added to a fiber web usingprocesses such as lamination, co-pleating, or collation. For example, insome cases, two layers are formed into a composite article by a wet laidprocess as described above, and the composite article is then combinedwith a third layer by any suitable process (e.g., lamination,co-pleating, or collation). It can be appreciated that a fiber web or acomposite article formed by the processes described herein may besuitably tailored not only based on the components of each fiber layer,but also according to the effect of using multiple fiber layers ofvarying properties in appropriate combination to form fiber webs havingthe characteristics described herein.

In some embodiments, further processing may involve pleating the fiberweb. For instance, two layers may be joined by a co-pleating process. Insome cases, the fiber web, or various layers thereof, may be suitablypleated by forming score lines at appropriately spaced distances apartfrom one another, allowing the fiber web to be folded. It should beappreciated that any suitable pleating technique may be used.

In some embodiments, a fiber web can be post-processed such as subjectedto a corrugation process to increase surface area within the web. Inembodiments in which a fiber web is pleated or corrugated, the depth ofthe pleats or corrugations may vary from about 0.01 mm to about 7 mm.For instance, the depth of the pleats or corrugations may be at leastabout 0.01 mm, at least about 0.1 mm, at least about 1 mm, at leastabout 2 mm, or at least about 5 mm, and/or less than or equal to about 7mm, less than or equal to about 5 mm, less than or equal to about 3 mm,or less than or equal to about 1 mm. Combinations of theabove-referenced ranges are possible. Other ranges are also possible.The periodicity of the pleats or corrugations may also vary, e.g., fromabout 2 cycles/inch to about 8 cycles per inch.

In other embodiments, a fiber web may be embossed or subject to adimpling process to produce protrusions and/or indentations in the fiberweb. In such embodiments, the depth of the protrusions or indentationsmay vary from about 0.01 mm to about 7 mm. For instance, the depth ofthe protrusions or indentations may be at least about 0.01 mm, at leastabout 0.1 mm, at least about 1 mm, at least about 2 mm, or at leastabout 5 mm, and/or less than or equal to about 7 mm, less than or equalto about 5 mm, less than or equal to about 3 mm, or less than or equalto about 1 mm. Combinations of the above-referenced ranges are possible.Other ranges are also possible.

It should be appreciated that the fiber web may include other parts inaddition to the one or more layers described herein. In someembodiments, further processing includes incorporation of one or morestructural features and/or stiffening elements. For instance, the fiberweb may be combined with additional structural features such aspolymeric and/or metallic meshes. In one embodiment, a screen backingmay be disposed on the fiber web, providing for further stiffness. Insome cases, a screen backing may aid in retaining the pleatedconfiguration. For example, a screen backing may be an expanded metalwire or an extruded plastic mesh.

In some embodiments, fiber webs used as filter media can be incorporatedinto a variety of filter elements for use in various filteringapplications. Exemplary types of filters include hydraulic mobilefilters, hydraulic industrial filters, fuel filters (e.g., automotivefuel filters), oil filters (e.g., lube oil filters or heavy duty lubeoil filters), chemical processing filters, industrial processingfilters, medical filters (e.g., filters for blood), air filters, andwater filters. In some cases, filter media described herein can be usedas coalescer filter media. The filter media may be suitable forfiltering gases or liquids.

The fiber webs and filter media disclosed herein can be incorporatedinto a variety of filter elements for use in various applicationsincluding hydraulic and non-hydraulic filtration applications includingfuel applications, lube applications, air applications, amongst others.Exemplary uses of hydraulic filters (e.g., high-, medium-, andlow-pressure filters) include mobile and industrial filters.

During use, the fiber webs mechanically trap particles on or in thelayers as fluid flows through the filter media. The fiber webs need notbe electrically charged to enhance trapping of contamination. Thus, insome embodiments, the filter media are not electrically charged.However, in some embodiments, the filter media may be electricallycharged.

EXAMPLES

The following examples are intended to illustrate certain embodiments ofthe present invention, but are not to be construed as limiting and donot exemplify the full scope of the invention.

Example 1

This example demonstrates a method of fabricating dual layer fiber websincluding a first layer comprising cellulose pulp fibers and a secondlayer comprising fibrillated aramid fibers.

Dual layer handsheets were made using a laboratory handsheet mold. Thefibers for the first layer were mixed in a blender with 1000 mL of waterfor 2 minutes. The slurry was placed in a handsheet mold and the fiberweb was formed on a wire. The fiber web was drained and dried. Then thefiber web was placed back into the handsheet mold, and the second slurrywas placed into the handsheet mold and formed on top of the first layer.The resulting fiber web was drained and dried. The resulting fiber websincluded a first layer comprising cellulose pulp and a second layercomprising fibrillated aramid fibers. The amount of material added forthe first layer was 18.9 g (HP-11 softwood pulp, HBA softwood pulp, andKuralon SPG-056 polyvinyl alcohol fiber in the ratio of [56.5:42.5:1])and the amount of material (100% aramid pulp) added for the second layerwas 3.8 g. The Canadian Standard Freeness for the fibrillated aramidfibers was an average of 80 mL.

The sample had a permeability of 2.5 CFM, a mean flow pore of 1.1microns, an average Multipass efficiency of 99.7% at 4 micron or greaterparticles, a dust hold capacity of 115 g/m², and a basis weight of 137.5lb/ream (with the second layer having a basis weight of 12.5 lb/ream andthe first layer having a basis weight of 125 lb/ream). Multipass FilterTests for determining efficiency and dust holding capacity wereperformed at 10 mg/L base upstream gravimetric level (BUGL), a facevelocity of 0.16 cm/s, a 200 kPa terminal pressure and a flow rate of 1L/min following the ISO 16889/19438 procedure. The Perm. Pore Indexvalue was 0.696.

This example shows that relatively high efficiencies at 4 microns can beobtained in fiber media including fibrillated fibers in one layer. Thisexample also shows that a relatively low Perm. Pore Index and arelatively high dust holding capacity can be obtained in such media.This example also shows that such efficiencies and dust holdingcapacities can be obtained in fiber webs that do not include any glassfibers.

Example 2

This example shows the fabrication of a wet laid fiber web including afirst layer comprising a mixture of Robur Flash (cellulose) fibers:HP-11 softwood fibers: PET (0.6 d×5 mm) fibers, and a second layercomprising fibrillated lyocell fibers. Several samples were made varyingthe level of fibrillation of the fibers in the first layer.

A wet laid papermaking process was used to fabricate dual layer fiberwebs. The first layer was formed on a Fourdrinier machine and drained,and the second layer was formed on top using another headbox. Theresulting fiber webs included a first layer comprising a mixture ofRobur Flash (cellulose) fibers: HP-11 softwood fibers: PET (0.6d×5 mm)fibers, and a second layer comprising fibrillated lyocell fibers. Thelyocell fibers in the second layer had an average Canadian StandardFreeness of 40 mL.

The weight ratios of the fibers in the first layer were 1:1:0.46 byweight. The basis weight ratios of the second layer to first layer werevaried, as were the conditions for refining (fibrillating) the fibers inthe first layer. The target basis weight for the combined layers was 60lb/ream for each sample. The following conditions were tested:

a. Sample 1: Second layer:first layer basis weight ratio of 1:2, with nofibrillation of fibers in the first layer.

b. Sample 2: Second layer:first layer basis weight ratio of 1:2 withsome fibrillation of fibers in the first layer. The Perm. Pore Indexvalue was 2.33.

c. Sample 3: Second layer:first layer basis weight ratio of 1:5, withsome fibrillation of fibers in the first layer. The Perm. Pore Indexvalue was 0.94. The above three conditions resulted in fiber webs havinga relatively low [mean flow pore (μm)/(permeability (cfm/sf))^(0.5)]values ranging from 1-3.

This example also shows that desirable Perm. Pore Index values can beobtained in fiber webs that do not include any glass fibers.

Example 3

Fiber webs were made using a combination of lyocell and eucalyptusfibers as a first, top layer. The first layer was formed on a second,bottom layer that did not include fibrillated fibers. Eucalyptus is ahardwood pulp with very small diameter and can help in obtaining a tighttop layer. The lyocell fibers in the first, top layer had an average CSFvalue of about 40 mL. The amounts of lyocell and eucalyptus fibers inthe first layer were varied. The basis weight of the first layer wasalso varied.

The basis weight of the second, bottom layer was 55 lb/ream layer andwas formed of Robur Flash (cellulose) fibers: HP-11 fibers: PET (0.6 d×5mm) fibers in the ratio 1:1:0.46 by weight. Table 1 shows the fractionof lyocell and eucalyptus fibers in the first, top layer, the basisweight of the first, top layer, and the resulting Perm. Pore Indexmeasured for each of the samples.

TABLE 1 Fraction of Fraction of Eucalyptus Basis weight of Perm. Lyocellfibers fibers in first, top layer Pore Sample in first layer first layer(lb/ream) Index* 1 0.5 0.5 20 1.02 2 0.5 0.5 20 1.01 3 0.5 0.5 10 1.00 41 0 10 0.69 5 0.5 0.5 20 1.00 6 0.5 0.5 10 0.93 7 0 1 10 1.91 8 1 0 200.83 9 0 1 20 2.23 10 0.5 0.5 10 1.02 *The Perm. Pore Index is measuredas [mean flow pore (μm)/(permeability (cfm/sf))^(0.5)].

This example shows that relatively low Perm. Pore Index values can beobtained by adding lyocell in combination with another pulp in a first,top layer. The Perm. Pore Index values obtained for the samples werebetween 0.8 and 2.25. This example also shows that such values can beobtained in fiber webs that do not include any glass fibers.

Example 4

This experiment shows that fiber media having different airpermeabilities can be achieved when varying the level of fibrillation oflyocell fibers in a first, top layer of a dual layer web.

The first, top layer included lyocell fibers and the basis weight of thelayer was varied between 10 lb/ream and 20 lb/ream in different samples.The second, bottom layer was made from HPZ, softwood kraft pulp andeucalyptus fibers in the weight ratio of 0.34:0.15:0.52 and remained thesame for all samples. The Canadian Standard Freeness (CSF) of thelyocell fibers in the top layer was varied and was 40 mL, 60 mL 200 mL,or 250 mL. The Perm. Pore Index values for each of the samples weremeasured as shown in Table 2.

The basis weight, air permeability, dust holding capacity, andefficiency at 4 microns was also tested for the fiber webs, as shown inTable 3. Multipass Filter Tests for determining efficiency and dustholding capacity were performed at 25 mg/L base upstream gravimetriclevel (BUGL), a face velocity of 0.06 cm/s, a 100 kPa terminal pressuresand a flow rate of 1 L/min following the ISO 16889/19438 procedure.

TABLE 2 Basis weight of Perm. top layer Pore Sample No. CSF (mL)(lb/ream) Thickness (mm) Index* 1 200 10 0.64 1.46 2 200 20 0.68 1.42 3250 10 0.63 1.57 4 250 20 0.71 1.55 5 60 10 0.61 1.19 6 60 20 0.65 1.217 40 10 0.62 0.96 8 40 20 0.68 0.81 9 No Lyocell 0 0.55 2.97 *The Perm.Pore Index is measured as [mean flow pore (μm)/(permeability(cfm/sf))^(0.5)].

TABLE 3 Dust Basis Air Perm. Thickness Holding Efficiency Sample weightPerm Pore at 20 KPa Capacity at 4 μm Nos. (lb/ream) (CFM) Index (mm)(g/m²) (%) 1 68.92 6.12 1.57 0.63 113.4 99.88 3 67.95 8.66 1.46 0.65137.99 99.71

This example shows that different air permeabilities can be obtainedwhen lyocell fibers having different levels of fibrillation are used ina first, top layer. The fiber webs have Perm. Pore Index values of lessthan 3. Furthermore, the fibers webs achieve high efficiency values.This example also shows that such values can be obtained in fiber websthat do not include any glass fibers.

Example 5

This example demonstrates a method of fabricating a dual layer fiber webincluding a first layer comprising cellulose pulp fibers and a secondlayer comprising fibrillated lyocell fibers, which was then collatedwith a meltblown layer positioned downstream of the second layer.

Dual layer handsheets were made using a laboratory handsheet mold. Thefibers for the first layer (10.8 g of cellulose fibers including 15%Prince George Pulp, 51% Eucalyptus fiber, 33% porosanier fiber) weremixed in a blender with 1000 mL of water for 2 minutes to form a firstslurry. The first slurry was placed in a handsheet mold and the fiberweb (i.e., the first layer) was formed on a wire. The fiber web wasdrained and dried. The fiber web was then placed back into the handsheetmold to act as a substrate for the second layer.

The second slurry contained 7.57 g of fibrillated lyocell pulp with 21%solids in 1000 mL of water. The average Canadian Standard Freeness forthe fibrillated lyocell fibers was 200 mL. The second slurry was placedinto the handsheet mold to form a second layer on top of the firstlayer. The resulting dual layer fiber web was drained and dried. Theresulting dual layer web had a basis weight of 107.4 gsm and an airpermeability of 15.4 cfm/sf.

A layer of meltblown fibers on a scrim having a basis weight of 36.8 gsmand an air permeability of 10 cfm/sf was collated with the dual layerweb to form an overall composite. The meltblown layer was positioneddownstream of the second layer of dual layer web in the composite. Theaverage fiber diameter of the meltblown fibers was 1 micron.

The composite had an air permeability of 6 cfm/sf, a dust holdingcapacity of 156 gsm, and a basis weight of 143.6 gsm. The initialefficiency of the composite was 99.47% at 4 micron or greater particles.The liquid filtration efficiency of the composite was 99.81% at 4 micronor greater particles. Multipass Filter Tests for determining initialefficiency, liquid filtration efficiency, and dust holding capacity wereperformed at 50 mg/L base upstream gravimetric level (BUGL), a facevelocity of 0.06 cm/s, and a flow rate of 1 L/min following the ISO16889/19438 procedure. The initial efficiency is the efficiency at 4, 5and 6 minutes after running the test. The liquid filtration efficiencyis the efficiency of the media after reaching a 100 kPa terminalpressure.

This example shows that relatively high dust holding capacities andefficiencies at 4 microns can be obtained in filter media includingfibrillated fibers in one layer and meltblown fibers in another layer.Comparable dust holding capacities and efficiencies were achieved withthe use of fibrillated fibers having lower freeness (e.g., CSF=200 mL)in this example, compared to media including fibrillated fibers havingrelatively higher freeness (e.g., average CSF values of 80 mL in Example1, 40 mL in Example 2, and 40 mL in Example 3). This example also showsthat such dust holding capacities and efficiencies can be obtained infiber webs that do not include any glass fibers.

Example 6

This example shows that filter media including a meltblown layer canimprove fuel-water separation efficiency of the media.

The procedure described in Example 5 was used to form a composite media.The composite media included a dual layer fiber web including a firstlayer comprising cellulose pulp fibers and a second layer comprisingfibrillated lyocell fibers, which was then collated with a meltblownlayer positioned downstream of the second layer.

The dual layer fiber web of this example had similar characteristics asthe dual layer fiber web described in Example 5, except the fibrillatedlyocell fibers had an average Canadian Standard Freeness of 100 mL.

The meltblown layer did not include a scrim, and had a basis weight of106 gsm, an air permeability of 25.8 cfm/sf, and an average fiberdiameter of 4-8 microns.

The composite including the dual layer fiber web and meltblown layer hadan initial liquid filtration efficiency of 99.5%, a liquid filtrationefficiency of 99.7%, and a fuel-water separation efficiency of 63.2%.Without the meltblown layer, the dual layer fiber web had a fuel-waterseparation efficiency of 32.5%.

It is expected that a fuel-water separation efficiency of higher than63.2% would be achieved with the media described in Example 5, whichincluded finer meltblown fibers (1 micron) compared to those of themeltblown layer in this example (4-8 microns).

Having thus described several aspects of at least one embodiment of thisinvention, it is to be appreciated various alterations, modifications,and improvements will readily occur to those skilled in the art. Suchalterations, modifications, and improvements are intended to be part ofthis disclosure, and are intended to be within the spirit and scope ofthe invention. Accordingly, the foregoing description and drawings areby way of example only.

What is claimed is:
 1. A filter media, comprising: a first layercomprising synthetic fibers; a second layer comprising glass fibers andfibrillated fibers; and a third layer comprising synthetic fibers and/orcellulose fibers.
 2. The filter media of claim 1, wherein the secondlayer and/or the third layer comprises a binder resin.
 3. The filtermedia of claim 1, wherein the first layer has a higher air permeabilitythan the second layer.
 4. The filter media of claim 1, wherein the firstlayer has an air permeability of greater than or equal to about 0.5cfm/sf and less than or equal to 1500 cfm/sf.
 5. The filter media ofclaim 1, wherein the third layer has an air permeability of greater thanor equal to about 0.5 cfm/sf and less than or equal to 1500 cfm/sf. 6.The filter media of claim 1, wherein the second layer has an airpermeability of less than or equal to 125 cfm/sf.
 7. The filter media ofclaim 1, wherein the third layer has a basis weight of greater than orequal to about 40 g/m² and less than or equal to about 500 g/m².
 8. Thefilter media of claim 1, wherein the first layer comprises meltblownfibers.
 9. The filter media of claim 1, wherein the second layer ispositioned between the first layer and the third layer.
 10. The filtermedia of claim 1, wherein the second layer and/or the third layer is wetlaid.
 11. A filter media, comprising: a layer comprising glass fibersand fibrillated fibers; wherein the layer has an air permeability ofless than or equal to 125 cfm/sf; wherein the layer has a mean flow poresize of greater than or equal to about 0.5 microns and less than orequal to about 50 microns; and wherein the layer comprises greater thanor equal to about 4 wt % and less than or equal to about 90 wt %fibrillated fibers.
 12. The filter media of claim 11, wherein the layeris wet laid.
 13. The filter media of claim 11, wherein the layer has abasis weight of greater than or equal to about 10 g/m² and less than orequal to about 200 g/m².
 14. The filter media of claim 11, where thefibrillated fibers have an average CSF of greater than or equal to about1 mL and less than or equal to about 800 mL.
 15. The filter media ofclaim 11, wherein the layer further comprises a binder resin.
 16. Thefilter media of claim 11, wherein the layer has a thickness of less thanor equal to about 2 mm.
 17. The filter media of claim 11, wherein thelayer has a Mullen burst strength of greater than 10 psi.
 18. The filtermedia of claim 11, further comprising an additional layer.
 19. Thefilter media of claim 18, wherein the additional layer has a higher airpermeability than the layer.